The answer C correctly uses possessive form and is the right answer. It's not A because there is only one George so the apostrophe is in the wrong place. In B, there's not even an apostrophe and it's not clear as to whether there is only one cousin or two or more cousins. In answer D, here should not be an apostrophe for develops.
Peak and top because crest means the top of mountain or hill
You can’t use third person without saying it’s your own research , but you can say “ people conducted their own research on this topic “
Terribly sorry if I'm wrong:
True
