The teacher often tells Jim and David _______ too much time _______ computer games.
A：not to spend, playing
B：not to spend, to play
C：don't spend, playing
D：shouldn't take, on
下列说法正确的是（ ）
关于腔肠动物，下列哪一项是错的（ ）
已知a=tan1，b=tan2，c=tan3，则（ ）
