Student or Learner
If the weather is fine, we'll go. If _________, __________.
A. not; not B. not; no
The answer is A, which puzzles me.
Is it natural from a native's point of view? What will you say as a form of omission?
Those are poor choices as far as I'm concerned as we would say "If not, we won't". However, of the two, A would be my choice, standing for "If not, we will not go."
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.