问题补充:
In the lecture, little Tom kept silent all the time unless to express his opinion.
A. he invited
B. he is invited
C. invited
D. being invited
答案:
A. he invited
B. he is invited
(答案→)C. invited
D. being invited
解析:句意:在演讲中,小汤姆一直保持沉默,除非他被邀请发表自己的看法。动作invite与其逻辑主语little Tom之间是被动关系,故用过去分词作状语,可知选C。