题目内容:
When you point out the purpose / problem of research again, the()is mainly used.
A.present tense
B.present perfect tense
C.past tense
D.future tense
参考答案:
When you point out the purpose / problem of research again, the()is mainly used.
A.present tense
B.present perfect tense
C.past tense
D.future tense