It was terribly windy last night and there was ___18-degree drop in ___ temperature.A.a;/ B./;/ C.an;/ D.an;the

D
A直接排除。 后面个选项，语感，

C，这里的temperature是表概念的抽象名词，不用冠词修饰。

B in temperature固定搭配。

C a drop in temperature 固定搭配

It was terribly windy last night and there was _an_18-degree drop in _x_ temperature.
18 - eighteen ,元音开头,用an
there is a drop in temperature ,是习惯表达.

C
a drop in temperature 固定搭配 temperature前不加冠词。