問題詳情
19 _________ to understand the body’s responses to weightlessness, as the data have grown in quantity and quality.
(A) In the past few decades have scientists begun
(B) Only in the past few decades scientists begin
(C) In the past few decades scientists are beginning
(D) Only in the past few decades have scientists begun
參考答案
答案：D
難度：困難0.264706
統計：A(8),B(5),C(9),D(9),E(0)