1.答案：B.
2.翻译：他说的话使得/导致我们感到害怕/恐惧.
3.
1）该句主语是一个从句,即what he said.
谓语含有一个固定搭配：cause sb to do sth,意思是“导致/使得某人做某事”,由此可以排除CD.
2）frightened意思是“感到害怕/恐惧的”,而frightening意思是“令人感到害怕/恐惧的”.
feel frightened的逻辑主语其实就是us,所以用frightened.
请楼上试着体会：I felt frightened about the frightening news.
我对这个令人恐惧的消息感到害怕.
由此排除A,B为正解.