The Dead Sea is so salty it’s hard for anything to live in it, is why it’s called theDea

The Dead Sea is so salty it’s hard for anything to live in it, is why it’s called the
Dead Sea.
A. that, which
B. that, that
C. /, that
D. /, what

(答案→)A. that, whichB. that, thatC. /, thatD. /, what解析：句意：死海是如此的咸以致于很难有生命在里面生存，那就是为什么它被称为死海。第一空是连词so…that如此以致于；which引导的是非限制性定语从句，先行词是前面的整个句子，what不能引导定语从句；that不能引导非限制性定语从句，故选A。

这个解释是对的