Have you noticed the problem he is now in low spirits？ come?A. where；WhatB. that；HowC. in

问题补充：

Have you noticed the problem he is now in low spirits？ come?

A. where；What

B. that；How

C. in which；For

D. what；As

答案：

A. where；What

(答案→)B. that；How

C. in which；For

D. what；As

解析：that引导同位语从句，用以说明problem的内容；后面的How come“怎么会那样”为固定搭配。