That was so serious a matter that I had no choice but ____ the police.

题目

That was so serious a matter that I had no choice but ____ the police.
(A) call in (B) calling in (C) called in (D) to call in
同时说明原因,

答案

D
but前面有一个否定词no,就形成了一个固定句型not……but
这个句型的特点是,but前面没有do,那but后用to+动词原形
but前面有do,后面就没有to
记起来也很好记,有to就没do,有do就没to