第一组：
The medicine is more effective that expected.
The medicine is more effective than is expected.
The medicine is more effective than it is expected.
第二组：
He has more money that expected.
He has more money than is expected.
He has more money than he is expected.
He has more money than it is expected.
第三组：
Don’t give him more money than necessary.
Don’t give him more money than is necessary.
Don’t give him more money than it is necessary.
这类句子都对吗？than干什么成分？标准结构是什么样呢？
第一组：
正：The medicine is more effective that expected.
正：The medicine is more effective than is expected.
误：The medicine is more effective than it is expected.
第二组：
正：He has more money that expected.
正：He has more money than is expected.
误：He has more money than he is expected.
误：He has more money than it is expected.
第三组：
正：Don’t give him more money than necessary.
正：Don’t give him more money than is necessary.
误：Don’t give him more money than it is necessary.
以上这几类句型的规范结构是：
than后面的 is, was 可以用也可以省略，但不可以加上主语，除非是用于 than itis/was expected / necessary that-从句或for sb to do sth句式（即it为形式主语，后面跟有外置的不定式主语或主语从句）。如：
The girls swam faster than it was expected that they would do.
再比较：
He arrived earlier than necessary.
=He arrived earlier than it was necessary for him to arrive.
