Question

________ these experiments were successfully completed would we think of going into humans.

A．If only

B．Only if

C．So that

D．Even if

Answer 1

B

试题分析：句意：只有这些实验完全成功以后，我们才会考虑把它应用于人类。根据“would we think of going into humans.”可知这个句子使用了部分倒装，所以用only+状语从句位于句首，选B。