Today, we had an exam and one of the questions was:

...... he exercised more and more, he developed stronger muscles.
a) What b) Since c) Whether d) As

I checked Since because I taught that the sentence could be "He developed stronger muscles because he exercised more and more". But after the exam, our teacher said that it's wrong and the correct option is As because both of these sentences point to same time. I understand his explanation but why it can not be what I say? In my opinion both of these options (Since and As) are correct. Am I really wrong? if so, why?

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    The emphasis in this sentence is on an ongoing process (more and more). As also can carry this meaning: while/during/etc. That's why it's the best choice. Commented Jan 18, 2015 at 12:14
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    There is nothing grammatically 'wrong' about using since in its because sense here (though in most conversations etc, because would be the more usual choice). However, logically, 'Because he exercised, he developed stronger muscles' seems to make much more sense than 'Because he exercised more and more, he developed stronger muscles'. One would expect 'Because he exercised more and more, his muscles kept on getting stronger'. Here, as user 103567 says, as almost certainly = while and is far more idiomatic. Commented Jan 18, 2015 at 12:15
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    @EdwinAshworth great comment, I almost understood this problem :) Commented Jan 18, 2015 at 12:19

2 Answers 2


You are right. Since is a possible answer here, meaning because, just as you suggest.

However, if the instruction or task is to choose the "best" answer, then as is "better".

The sentence uses the phrase more and more, which suggests a process of increasing over time. As can mean while so is more likely in the sentence.

If we began with Since, meaning because, we'd more likely leave out more and more or say something like Since he exercised more and more, his muscles became more and more developed.

Note: In any case, learning facts like "differences between as and since is a very inefficient way to improve English proficiency. All possible such rules in English are endless in number and complexity. Reading more things you like at a level that's easy for you is much better.

  • "Why are you wearing a T-shirt at work as it is forbidden" is 'as' correct here! Commented Jun 26, 2019 at 10:00
  • It might be "correct", but that is a question and needs to end with a question mark. Tiny any case it's at least a bit odd, and native speakers of American and British standard English would be much more likely to ask in another way, for example, Why did you wear a T-shirt at work? It's forbidden. or You shouldn't have worn a T-shirt to work, because it's forbidden. In fact forbidden is a rather formal term for ordinary speech. *Why did you wear that T-shirt? It's against the rules. would also be more common. Commented Jun 29, 2019 at 3:54
  • @Kumarsadhu If you can comment, you know not to do that to ask supplementary questions.
    – Andrew Leach
    Commented Jun 29, 2019 at 7:38

Here you use "as" in the sense of "while", not "because".

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    Hi, and welcome to the site. It's common here to support your answer with sources, even on an 'easy' question. That makes your answer stronger, and more likely to be viewed as correct. Otherwise, even if it's correct, it's likely to be viewed as only opinion. The site tour and the help center will give you guidance on how to use this site. Commented Jan 18, 2015 at 12:12
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    I agree that both "as" and "since could be used, depending on the meaning without any problems of tenses.
    – Martin
    Commented Jan 18, 2015 at 12:13
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    This does not answer his question. Why cannot we say Since...? Commented Jan 18, 2015 at 12:34
  • Because it makes the sentence sound strange.
    – user103567
    Commented Jan 18, 2015 at 13:10

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