The first thing you should do is to learn all the new words by heart.A. whatB. thatC. whi

问题补充：

The first thing you should do is to learn all the new words by heart.

A. what

B. that

C. which

D. who

答案：

A. what

B. that

C. which

D. who

解析：先行词被序数词、形容词的最高级及only, any, few,little, no, all, very,last等修饰时,关系代词常用that不用which。