A:充分而不必要条件
B:必要而不充分条件
C:充分必要条件
D:即不充分也不必要条件
The art club is for members only. You can't go in _______ you are a member.
一块农田中的农作物可以看做一个生态系统。
Look at the man over there.He is hands at us.