A:充分不必要条件
B:必要不充分条件
C:充要条件
D:既不充分也不必要条件
如图,在Rt△ABC中,∠ACB=90°,D,E,F分别是AB,BC,CA的中点,若CD=5cm,则EF为( )
A:I called you yesterday. You didn't answer it. B:Oh, sorry. I_ in the bathroom at that time.
世界上绝大多数动植物都能在我国找到适合生长的地区,主要是因为我国( )
对人工种子正确的解释是( )