this sentence a second time the meaning will become clear to you.A. If readingB. When yo

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。