First conditional or second conditional?

Which is more correct to combine the following two sentences with 'if': first or second conditional?

He won't study hard, so he won't get high marks.

Thanks.

The first conditional is appropriate here:

If he doesn't study hard, he won't get high marks.

(It would also be possible to say "If he won't study hard, he won't get high marks". Here, "won't" is best understood not as a reference to future time but to willingness = "if he isn't willing to study hard".)

The second conditional is possible but changes the meaning:

If he didn't study hard, he wouldn't get high marks.

His failure to study hard becomes a hypothetical. There is now an implication, assumption or suggestion that he will study hard, which contradicts your original sentence ("He won't study hard...").

• In the original question, the teacher asked the students to choose the correct answer as follows: He won't study hard so he won't get high marks. If he (studies-studied-had studied-was studying) hard, he (will get- would get- would have got- get) high marks. That means the options are not correct. Right? Oct 6, 2017 at 23:15
• Well, the question you asked was how to combine the two clauses in a conditional. That doesn't involve removing the negation. This obviously isn't necessary in order to combine them, so I don't understand why that has been done. With those options, I find it tougher: it could be "If he studies hard, he will get high marks" (preserving the future form in the second clause) or it could be "If he studied hard, he would get high marks" (preserving the suggestion that he won't study hard and that this therefore won't happen - perhaps this is therefore the more likely answer). Oct 7, 2017 at 8:52
• First, you're right. I should have asked the question in a direct way. Second, l'm grateful that you replied to the comment. Some of my friends go with your second version, conditional 2. Oct 7, 2017 at 10:45

Second conditional is the only one that can convey that meaning.

A first conditional sentence combining those two clauses looks like this:

If doesn't study hard, he won't get high marks.

The problem is this sentence allows the possibility that he might study, whereas your original sentence does not. It states he will not study and as a result will not get high marks, so first conditional cannot work.

A second conditional version looks like this:

If he studied hard, he could get high marks.

As with the original, this sentence means he will not study hard and therefore will not get high marks. I used "could" rather than "would" because the original doesn't suggest he would certainly get high marks if he studied, just that he won't get high marks because he won't study.