He was sure she had got the job.____ a letter of refusal came, which hecertainly wasn't expecting.[A] Then[B] When[C] Thus[D] Therefore答案是A____ a letter of refusal came, which hecertainly wasn't expecting.这里句子结构我不太明白。首先，后面那句，谁是主句。。谁是从句？从句又是什么从句？然后。。这题具体判断思路是怎样的呢？句子意思我明白，但判断选择那个一点头绪都没有。偶很菜。。麻烦尽可能让偶理解方式讲讲，谢谢。
參考答案:which he certainly wasn't expecting.
非限制性定语从句，修饰the letter
我用排除法给你解释一下哈
首先，B被淘汰，原因是when是引导连词，这句显然不需要任何引导词来引导句子，因为后面已经有了which引导的非限制性定语从句，前面是主句。
其次，CD都是表示因果关系的副词，这两个句子间有任何因果关系吗？没有，所以排除也。
最后，就剩下A是正确答案了。
解释得不好，可以参考哈
