---He ought to have been warned of the danger.
--- , but he wouldn’t listen to me.
A. He did
B. He should
C. He ought to
D. He was
网友回答
A. He did
B. He should
C. He ought to
(答案→)D. He was
解析：考查特殊句式。So + 主语+ 助动词/系动词/情态动词，表示“的确如此”。根据答语后半句可知空处表示他的确被警告了，因此选D。