问题补充:
this sentence a second time, the meaning will become clear to you.
A. If reading
B. When you read
C. Reading
D. Read
答案:
A. If reading
(答案→)B. When you read
C. Reading
D. Read
解析:通过分析句子结构,其中含有一个时间状语从句,表示“当……时候”,A选项缺主语,C选项和D选项和句子主语不存在逻辑上的关系,故排除,故选B。