The correct answer is D.
Girls in general tend to spend more time with friends. This isn't to say that boys don't spend a lot of time with their friends but girls tend to engage more in their social relationships, whereas boys spend more time in competitive sports, more time in clubs and less time engaging in social relationships.
The answer is Habitat. I'm 100% sure it is.
The answer is (C) Replication
Though occasional errors could occur in cells during replication; the cells have error checking and proofing mechanisms that reduce the rate of error to one to several million replications in higher eukaryotes.
After all, one mismatch error during replication would not result in major effects. The others choices, however, have higher rates of causing genetic abnormalities.