It______12rabbitstotestasampleofvaccine,nowittakesonly6.
A.usedtotaking
B.usedtotake
C.isusedtotake
D.wasusedto
正确答案:B答案为B。过去曾经需要12个兔子测试疫苗样本,现在只需要6个。usedtodo“曾经”;beusedtodoingsth.“习惯于做某事”。

It______12rabbitstotestasampleofvaccine,nowittakesonly6.
A.usedtotaking
B.usedtotake
C.isusedtotake
D.wasusedto
正确答案:B上一篇 If there are any new words, ______ in a dictionary.A. look them through B. look them
下一篇 The idea for the new project came to Jack ______ to his study recently.A. while devoti