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
网友回答
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。