It is...that…句式通常不能强调哪些成分
有这样一道考题：
It was a teacher that she __________.
A. was B. seemed C. looked D. married
此题应选D。从句意上看似乎4个选项都行，其实这里只能填D。因为填A，B，C 中的任意一个选项，都会导致句中的 a teacher成为表语，然而按照强调句句法规则，It is...that这一强调句型是不能强调表语的。一般说来，以下成分不能用于强调句中的被强调部分：
1. 表语：
她很美。
正：She is beautiful.
误：It is beautiful she is.
他是医生。
正：He is a doctor.
误：It is a doctor that he is.
但是宾语补足语却可以用作被强调部分：
他们选他担任主席。
正：They elected him chairman.
正：It was chairman that they elected him.
2. since 和 as 引导的原因状语从句(但 because 从句却可以)：
他不能来是因为他病了。
正：It is because he is ill that he can’t come.
误：It is since[as] he’s ill that he can’t come.
3. although 引导的让步状语从句：
虽然累了，但他还是去了。
正：He went although he was tired.(www.hxen.com)
误：It was although he was tired that he went.