問題詳情

40. A series of experiments to test the new drug _______ carried out, but so far it still can’t prove to be an
effective drug.
(A) was
(B) were
(C) has been
(D) have been

參考答案

答案：C

統計：A:55,B:48,C:203,D:140,E:0

難度：適中