In my opinion,life in the twenty-first century is much easier than_______.

In my opinion,life in the twenty-first century is much easier than_______.
A.that used to be B.it used to be
我觉得应该选B,但是答案选的是A.
这是个什么从句啊?为什么be后面不加that作表语呢?
对不起，我打错了。
应该是
In my opinion,life in the twenty-first century is much easier than_______.
A.that used to be B.it used to be
我觉得应该选A，但是答案选的是B。
这是个什么从句啊？为什么be后面不加that作表语呢？