Peter doesn't go to the party today because it rains heavily.

=>If

I can't help you because you don't tell me your problem.

=>If

We won't have a holiday because we don't have enough money.

=>If

We can't go out because it is raining.

=>If

Ben is not intelligent enough to answer your question.

=>If

If you don't speak loudly, he won't hear anything.

=>Unless

My students (do)___ Math at the moment.