---nothing to talk about,he said good-bye and went out of th

很高兴为你解答.
保证正确率~!
正确答案是：A
【解析】：
这里是独立主格做原因状语,等于：
Because there was nothing to talk about,he said good-bye and went out of the room.
there 是逻辑主语,因为从句的主语和主句的主语不一致,主句的主语不是动作的发出者.
【翻译】：因为没什么好说的,他说了声“再见”,然后走出了房间.
祝开心~!
再问： 那B选项呢?
再答： 选B项的话，它的主语应该就是he，但是只有he has nothing to talk about ，没有 he is nothing to talk about ，故是错误的，正确答案是A。如果是选having nothing to talk about ，也是正确的，但是题目没这个选项。