Answer:
Option A, Gene Selection
Step-by-step explanation:
Gene selection is a process by which some specific trait with in an organism become more extensive than other traits. As in the given case , grey color cats are being produced more frequently in the coming generation even when two black cat species interbreed. This means somewhere the two black cats have some other color allele (not expressed earlier) which expresses itself more extensively in the later generation.
Hence , option A is the correct answer