问题补充：
“Was it under the tree you were away talking to a friend?” “Sure. But when I got back there, the bike was gone.
A. that
B. where
C. which
D. while
答案：
A. that
B. where
C. which
(答案→)D. while
解析：做好此题的关键是正确理解上下文的语境。在此句中，it 是代词，指代 the bike，句意为：“当你离开去同朋友谈话的时候，你的自行车是在这树下吗?”“当然，但当我回来时，自行车就不见了。”现在反过来分析一下，假若选A，将此句判为强调句，句子即为 Was it under the tree that you were away talking to a friend? 若进一步转换为非强调句，句子则为 Under the tree while you were talking to a friend，句意显然很荒唐。
