20.______ that caused him to serve dinner an hour later than

B

此题容易认为强调的是原因状语从句 because we were late。但实际上，此题的答案为B，强调的是句子主语 our being late，此题若还原成非强调句，即为：Our being late caused him to serve dinner an hour later than usual. 注意，强调句的一个显著特点是，若去掉强调结构 it is [was]… that…，句子仍然成立；换句话说，该结构中的 it is [was]… that… that 不能充当句子成分，而实际上句中的动词cause需要有自己的主语。