（）used to be considered impossible has now turned into realities.
A、
this
B、
that
C、
what
D、
whatever
【正确答案】：C
【题目解析】：
本题考查的是主语从句的引导词的用法，从句中缺少主语用what引导。句意为：过去认为不可能的事情现在变为现实了。
（）used to be considered impossible has now turned into realities.
（）used to be considered impossible has now turned into realities.
this
that
what
whatever
本题考查的是主语从句的引导词的用法，从句中缺少主语用what引导。句意为：过去认为不可能的事情现在变为现实了。