Mammals. I am no scientist, but I think that they are closer to mammals due to the fact that they are warm-blooded, and they raise their young. Reptiles are cold blooded and usually leave their offspring to fend for themselves.
Birds aren't just closely related to dinosaurs, they are really are dinosaurs this is what most people mean when they say that birds are reptiles, although technically according to the phylogenetic system mammals are also reptiles.
The sorting of genes during sexual reproduction results in a large amount of genetic variation.because the primary advantage sexual reproduction has against asexual reproduction because of genetic diversity B is the right option hope this helps
