B is simply invalid, in that if he doesn't do this refers to a [possible] future condition, so there's no grammatical or semantic way to couple this to [then] she wouldn't be doing that, which refers to [actual] current activity.
A and C are grammatically credible, but A is semantically unlikely. Perhaps it will help to consider a different version of the basic format IF [statement1] [statement2]...
A1: If you did not kill him you wouldn't be on trial for murder
C1: If you had not killed him you wouldn't be on trial for murder
A1 can be paraphrased You must have killed him or you wouldn't be on trial, the same construction as If you didn't love me you wouldn't have married me. Since statement2 is true, statement1 must be true too.
C1 can be paraphrased the reason you are on trial is because you killed him. In some hypothetical scenario where statement1 isn't (or wasn't) true, statement2 isn't (or wasn't or won't be) true either. See the final paragraph in this related answer for more on why isn't/wasn't/won't be are to some extent interchangeable in the "irrealis inferential conditional" context of that preceding sentence.
OP's last option is grammatically valid, but an unlikely form in most contexts. But it would work in, say,...
D1: If he wasn't boring me I wouldn't be thinking about leaving the party
Some people would say that should be If he weren't boring me..., but it's a common informal usage.
TL;DR: C is the "best" answer, but A and D are at least "credible" in contrived contexts. I don't think it's a good idea for multiple choice questions like this to offer more than one "grammatically valid" alternative.