A. when B. that
C. which D. in which
【陷阱】容易误选B，误认为这是强调句。
【分析】其实，此题应选A，这不是强调句。因为在强调句中，若去掉强调句的结构词 it is [was]…that…，句子结构仍然完整，但此句不是这样，若去掉结构词，即为 Five o’clock the fire broke out，句子不完整，但若在five o’clock前加上介词at则可以，因为 at five o’clock 用作时间状语。此题选A可分析为：it 表时间，when the fire broke out 为时间状语从句，全句意为“火灾是5点钟发生的吗?”比较下面一题（答案选B，为强调句）：
Was it at five o’clock ______the fire broke out?
A. when B. that
C. which D. in which
题5：It’s more than half a century _____ my grandfather joined the Party and became a servant to the people.
A. when B. that
C. since D. while
【陷阱】容易误选B，认为这是强调句型。
【分析】假若选B，将此句分析为强调句，那么若将此句还原为非强调句就应该是My grandfather joined the Party and became a servant to the people more than half a century. 很显然, 句中的 more than half a century 是一段时间，然而它修饰的谓语动词 joined…became 却是两个终止性动词，这显然不合适。其实，此题应选C，属于“It is＋一段时间＋since 从句”句型，句意为“我爷爷加入党组织成为人民的公仆已有半个多世纪了”。此句的主句谓语也可以用现在完成时态(has been)，但在口语中多用一般现在时代替。
题6：It was lack of money, not of effort, _____ defeated their plan.
A. which B. as
C. that D. what
【陷阱】容易误选A，受空格前逗号的影响，误认为这是一个非限制性定语从句，从而误选了A。
【分析】其实，此题最佳答案为C，整个句子为强调句，被强调成分为 lack of money, not of effort。由于句中插入 not of effort 这一结构，干扰了许多同学对 it was lack of money that defeated their plan 这一强调句的认识和理解。