问题补充：
Tom hid himself behind the door, he could hear the steps of his mother clearly.
A. from which
B. from where
C. where
D. which
答案：
A. from which
(答案→)B. from where
C. where
D. which
解析：句意：汤姆把自己躲藏在门后面，从那里他能清楚地听到他母亲的脚步声。where表地点，在这里代替 behind the door，做介词from的宾语，相当于from behind the door，which是关系代词，那一个，代替是物的先行词，作主语、宾语或者表语。选择定语从句关系词的一个依据是，看关系词在从句中所做的成分。故选B。
考点: 考查定语从句的用法。
