A:that
B:what
C:which
D:where
下列有关癌细胞的叙述正确的是
When you get out of the taxi,make sure that none of your possessions are________.
设s,t是非零实数,i→,j→是单位向量,当两向量si→+tj→,ti→-sj→的模相等时,i→,j→的夹角是( )