以下这道题``选哪个?We must make some investigations we can draw any concl_英语解答

以下这道题``选哪个?We must make some investigations we can draw any conclusion.
We must make some investigations we can draw any conclusion.
A.since
B.before
C.until
D.when

人气：444 ℃　时间：2019-11-01 07:51:22

解答

选before
意思为在我们可以得到任何结论之前必须作出一些研究.