How can you normally tell if 2 things can interbreed

Species can interbreed if they generally have similar external appearances and internal physiology. What this simply means is that species can preferably mate with their same species because of the attraction that is naturally built within their frames. Other scientists suggest that interbreeding is possible because nature sees ways on how to make viable offsprings that can carry on the continuity of the species.

The answer would be b. it is a learned trait