问题
单项选择题
The fire brigade arrived two hours later after the alarm was sounded,______it was too late to save much of the building.
A．then
B．when
C．which
D．though
答案
参考答案：B
解析：题中要求填进一个具有连接作用的词，将前后两个句子连起来，所以首先排除then；分析前后两个句子之间的关系得知，though也是不对的，因为此处显然不是转折关系；which， when引导非限制性定语从句，故接下来关键是要找出哪个词是先行词，很明显是two hours later，所以应该选when，表示时间“这时”。