问题
选择题
While________ along the road, Mr. Smith met an old friend of his.
A．walked
B．he is walking
C．walking
D．is walking
答案
答案：C
题目分析：考查状语从句及其省略。句子可还原成由while引导的时间状语从句，While he was walking along the road, Mr. Smith met an old friend of his.故B错误在is应改成was。状语从句的省略是指省略从句的主语和部分谓语，即省略he was，故选C