Conjunctions

A. because ✓
"Because" is correct—it introduces the reason or cause for why you couldn't sleep. The sentence structure is: main clause + "because" + reason.

B. so ✗
"So" shows a result or consequence, not a reason. It works backwards: "It was too hot, so I couldn't sleep"—but not "I couldn't sleep so it was too hot."

C. as ✗
While "as" can mean "because," it's less direct and more formal. It's possible but "because" is the clearer, more natural choice for everyday English.

D. why ✗
"Why" is a question word, not a conjunction. You can't use it to connect clauses this way ("couldn't sleep why..." is grammatically incorrect).

Why A (as) is correct:
"As" means "because" here—it explains the *reason* for his exhaustion. The sentence means: "He was exhausted *because* he had been working all day."

Why the others are wrong:
- B (while) means "at the same time as," which doesn't explain *why* he was exhausted, just when it happened
- C (until) means "up to the point that," which doesn't fit the meaning
- D (when) also just marks *when* something happened, not the reason—it would feel incomplete ("He was exhausted when he had been working all day" doesn't explain cause and effect)

Why A is correct:
"Why" asks for the reason or cause. She couldn't understand the reason/cause of his anger—this is the logical meaning needed here.

Why the others are wrong:
- B (so): "So" means "therefore" or "in order to." "She couldn't understand so he was angry" doesn't make grammatical sense.
- C (which): "Which" is used to ask about choices from a group. There's no choice being made here—we need a reason.
- D (when): "When" asks about time. We're not asking when he was angry, but rather why he was angry.

A. before ✓
"Before" means finishing the project earlier than the deadline—this makes sense because you want to complete work on time or early, not miss the deadline.

B. after ✗
"After" means finishing *past* the deadline, which defeats the purpose of having one.

C. until ✗
"Until" suggests you work continuously up to the deadline point, but doesn't clearly express the goal of finishing by that time.

D. while ✗
"While" means during the same time as the deadline, which is vague and doesn't indicate completion before the deadline passes.

Correct answer: A. before

"Before 4 PM" means anytime prior to that time—this works perfectly because you're asking someone to call you at any point earlier than 4 PM.

Why the others are wrong:
- B. as – "as 4 PM" doesn't make sense; "as" means "while" or "at the same time as," which is awkward here
- C. when – "when 4 PM" is grammatically incorrect; you'd need "when it's 4 PM" (too wordy)
- D. where – "where 4 PM" makes no sense; "where" refers to place, not time

A. Whenever ✓
This is correct because "whenever" means "at any time that" — it expresses that she will call you at the moment she gets news. It fits the meaning perfectly.

B. So ✗
"So" shows cause/effect ("she will call me so...") but doesn't fit here. You need a time word, not a reason word.

C. Which ✗
"Which" is a relative pronoun used to describe things, not to show time. It doesn't make sense in this sentence structure.

D. Until ✗
"Until" means "up to the point when" — it would suggest she'll keep calling you up until she has news, then stop. The wrong time relationship.

Until is correct because it shows you'll wait for the entire duration up to the point when the exam finishes—it marks the end point of the waiting period.

• As long as means "during the time that" something continues, but here we need to show waiting up to a specific endpoint, not during a condition.
• So is a conjunction showing result/consequence ("I was tired, so I slept"), which doesn't fit this time relationship.
• When refers to a specific moment in time, but "I'll wait for you when you finish" suggests waiting *at* that moment, not *until* that moment arrives.

A. so ✓
"So" shows a cause-and-effect relationship: the headache (cause) leads to taking medicine (effect). This is the logical connection the sentence needs.

B. which ✗
"Which" is a relative pronoun used to add extra information about a noun, not to connect two related actions.

C. until ✗
"Until" shows a time limit ("I'll wait until you arrive"), not a cause-and-effect relationship. This doesn't fit the meaning here.

D. why ✗
"Why" is a question word asking for a reason, not a connector that joins two clauses together logically.

# Explanation

A. as ✓ Correct
"As" means "because" here—it explains the *reason* you couldn't sleep. The sentence reads naturally: "I couldn't sleep because I was too excited."

B. which
"Which" is a relative pronoun used to add extra information about a noun, not to show cause-and-effect. It would create a grammatically awkward or incorrect sentence.

C. before
"Before" shows *time order*, not reason. "I couldn't sleep before I was too excited" doesn't make logical sense.

D. until
"Until" also shows time order, meaning "up to the point when." It would suggest you eventually slept once you stopped being excited, which isn't what the sentence intends to express.

Until is correct because it shows we waited for a specific point in time (when the rain stopped), then we went out. It connects two events in sequence.

• Which is a relative pronoun for describing things, not for showing time relationships.
• Why asks for a reason, not a time connection.
• While means "during the time that" (simultaneous events), but we didn't go out *while* it was raining—we went out *after* it stopped.

A. where ✓
"Where" is correct because the sentence needs a location. You're saying you don't remember the *place* you left your keys—this is the missing information.

B. until ✗
"Until" refers to time or a deadline, not location. "I don't remember until I left my keys" doesn't make grammatical sense.

C. why ✗
"Why" asks for a reason. While you might forget *why* you left keys somewhere, the sentence structure here needs a location word.

D. while ✗
"While" means "during the time that," but it doesn't fit here. You need a question word, not a time connector.

While is correct because it shows two actions happening at the same time—he cooked and you cleaned simultaneously.

Why the others don't work:
- Which is a relative pronoun for describing things, not for connecting two actions
- Who is for people/subjects, not for linking clauses about timing
- Until shows when something *stops*, not two things happening together ("until I cleaned" would mean he stopped cooking when you started cleaning, which doesn't match the intended meaning)

A. because ✓
This shows the *reason* she couldn't go—work was the cause of her absence. This is what the sentence needs.

B. until ✗
"Until" shows timing ("she couldn't go until she finished work"), but here we need a reason, not a time condition.

C. why ✗
"Why" is a question word, not a conjunction. It doesn't connect two clauses this way.

D. while ✗
"While" means "at the same time as," suggesting both things happened together, not that one caused the other.

A. because ✓
This shows the *reason* why you went to the beach (the sunny weather caused you to go). It connects a cause to a result.

B. which ✗
This is a relative pronoun used to add extra information about a noun, but it doesn't show a reason. "We went to the beach which it was sunny" doesn't make grammatical sense.

C. before ✗
This shows *time order* (something happening earlier), not reason. It would mean the beach trip happened before it was sunny, which contradicts the sentence.

D. after ✗
Like "before," this shows time order (something happening later). It would mean you went after it was sunny, which doesn't fit the intended meaning.

So that (A) is correct because it shows purpose — you study every day in order to achieve the goal of improving your English. It answers "why do you study?"

• Where (B) — wrong; it refers to a place, not a reason or purpose
• Why (C) — wrong; it's a question word, not a connector that joins two clauses
• While (D) — wrong; it means "at the same time," not purpose (e.g., "I study while eating" = simultaneous actions)

Correct Answer: A. so that
This phrase shows *purpose* — we left early *in order to* avoid missing the train. "So that" correctly introduces a clause explaining why the action was taken.

Why the others are wrong:
- B. which — This is a relative pronoun for describing things, not for showing purpose or reason.
- C. before — This shows *timing* (one thing happens before another), not the reason or goal behind an action.
- D. after — This also shows timing, and doesn't make logical sense here (we couldn't leave after to prevent missing the train).

A. when ✓
This is correct because "when" introduces a time clause, and the sentence means "I'll call you at the time that I arrive at the airport."

B. which ✗
"Which" is a relative pronoun used for things, not for showing time relationships.

C. until ✗
"Until" means "up to the point that something happens," so this would mean you won't call before arriving—but you'd call at that moment, which is awkward here.

D. why ✗
"Why" asks for a reason, not a time, so it doesn't fit the sentence structure or meaning.

Why A is correct:
"Either...or" presents two choices and means you can pick one option or the other. It fits perfectly here: "you can choose either coffee or tea" (pick one).

Why the others are wrong:
- B (or, either): Wrong word order. "Either...or" must come in this sequence, not reversed.
- C (neither, nor): This means *not one and not the other*—it would say you can't have coffee or tea, which contradicts the meaning.
- D (both, and): This means you get both options together, not a choice between them.

Although is correct because it shows contrast—it connects two opposite ideas (rain vs. having fun). The sentence means "despite the rain, we had fun."

While is wrong here because it means "at the same time as," not "in spite of." It would suggest the rain and fun happened together without showing the contrast.

Because is wrong because it shows cause and effect. "Because it rained, we had fun" doesn't make logical sense—rain wouldn't be the reason we had fun.

As is wrong because it means "at the time that" or "in the way that," not "despite." It doesn't capture the contrasting idea.

Why "as" is correct:
"As" means "because" and shows the reason for your absence. The sentence logically explains: you'll be absent *because* you're traveling.

Why the others are wrong:
- "when" — Shows timing, not reason. "When I'll be traveling" doesn't explain *why* you're absent.
- "although" — Shows contrast (like "even though"). This would wrongly suggest traveling shouldn't cause absence.
- "but" — Shows contradiction. This would suggest absence and traveling are opposing ideas, which doesn't make sense.