假设法

　　如果对单项选择题的选项感到困惑，而又难以突破时，我们可以换一个角度，从"假设某项成立"出发，结合题意，进行分析推理，从而打开解题思路，变难为易。

　　4. It was 3 o'clock _____ they arrived at the station.

　　A. that B. when C. after D. before

　　该题正确答案为B. 但很多学生认为这是强调句而选A. 现在假设A选项成立，即：It was 3 o'clock that they arrived at the station. 根据强调句的验证方法，去掉it was…that… 即变为：3 o'clock they arrived at the station. 这显然是错的。因为3 o'clock前缺少介词at 故假设不成立。it在此不属于强调结构，而是指代时间的无人称代词。而选B则是由when引导的时间状语从句。意思为"当他们到达车站时，时间是3点钟。"

　　5. Is this the factory ____ you visited the other day?

　　A. the one B. that C. where D. why

　　对于此题，有些学生选C. 理由是这个定语从句的先行词表示地点。现在假设C是正确的，即Is this the factory where you visited the other day?而在定语从句中的谓语动词visited为及物动词，一定要带宾语，但where是副词，不可能充当宾语，所以假设不成立。由此分析，而得出正确答案应为B.

　　6. _____ he really means is that he disagrees with us.

　　A. What B. That C. Why D. If

　　对于此题，考生不知选A还是选B. 其实答案为A. 现在假设B是正确的，即That he really means is that he disagrees with us. 这样That he really means为一个主语从句，mean为及物动词，缺少宾语，因为that只是起到连接作用，而不能充当宾语，所以假设不成立。

　　当解题感到困惑时，可以假设某选项为正确答案，将此答案填入句中，对全句结构进行分析。这对解题可以起到良好的启迪和导向作用。