Subsets that are subspaces of P2

Hello, i recently took a linear algebra test and there was a bonus on it. The bonus was the material that we are going to soon be learning. I have not read ahead so i didnt get it right. I was wondering if you guys could explain it to me.

Bonus:

Which of the following subsets of P2 are subspaces of P2?

A.) p(t)| p'(t)+2p(t)+7=0

B.) p(t)| p(8)=0

C.) p(t)| integral from 0-1(p(t)dt)=0

D.) p(t)| p(7)=4

E.) p(t)| p'(4)=p(0)

F.) p(t)| p(-t)=p(t) for all t

Thank You,

Diggidy