问题
选择题
The plan for the new design occurred to Mr. Smith______on his work recently.
A．while concentrated
B．while concentrating
C．while he concentrated
D．while concentrating himself
答案
答案：C
C 此题易选B, 认为题干是个省略句, 过去分词作时间状语。如果是省略句的话，省略的成分应该与的主句的主语和be动词相同，而且主句的主语是the plan，显然是不能作过去分词concentrated的逻辑主语的。