Ⅰ.Goals:
1. Help Ss to know more about attributive clauses.
2. Help Ss learn about the attributive clauses introduced by a preposition+ which and a preposition+ whom and make sure they know in what circumstances these two forms are used.
Ⅱ.Self-study:
思考：
1. In the dark street, there wasn’t a single person _________ they could turn for help.
A. whom B. who C. to whom D. from whom
