将水稻、西瓜、松树归为一类，把海带、地钱和蕨归为另一类．这种分类的依据是（　　）

A．有根或无根

B．有种子或无种子

C．水生或陆生

D．有果实或无果实

There was a (an) __________ silence between us after we were left alone in the sitting-room.

A．awkward

B．angry

C．adequate

D．patient