一道高中单选题

as（so）....as.....
so....that....
两个组合分别是什么意思，仔细想想就没明白了，尤其是第一个组合，当表示否定时，多用so！

AS 在这里表示的是原因,而that 没有这样的功能.

你选A，可能是把that 作同位语了，但work out 后应接宾语，as 则正好充当宾语

这是as引导的定语从句.
as引导定语从句的两个重要用法:
1.当先行词被such修饰时.
例:He is not such a studentas would leave his work half done.
例:As a teacher,I seldom give my students such a difficult problem as they can not work out.
此句相当于As a teacher,I seldom give my students so difficult a problem as they can not work out.
2、as引导非限定性定于从句。as在定于从句中作主语、表语或宾语，这个定于从句说明整个句子，可以放在主句之前。如：As we all know, he studies very hard.
所以该题选D.

that引导的是从句
so as to
so that一句句子