问题
选择题
_______, the experiment will be successful.
A．If carefully doing
B．If it done carefully
C．If carefully done
D．If doing carefully
答案
答案：C
题目分析：考查省略。在if引导的条件状语从句中，省略了主语和be动词，experiment与do之间是被动关系要用被动语态，即完整句子应该是，If the experiment is done carefully。所以答案选C。