English films is a good way to learn English. So some films, please.
A:Watch; watch
B:Watching; watch
C:Watching;watching
若用反证法证明命题:“若实数a、b满足ab=0,则a、b中至少有一个是0.”第一步应假设____.
下列有关细胞分裂的叙述,正确的是( )