■ The buses, most of _______ were already full, were surrounded by an angry crowd.
A. that                                   B. it
C. them                                 D. which
【易错】容易误选 C，用 them 代指 the buses。
【分析】最佳答案是D。most of which were already full 为非限制性定语从句，修饰 the buses。类似地，以下各题也选D：
(1) His house, for _______ he paid $10, 000, is now worth $50, 000.
A. that                                   B. it
C. them                                 D. which
(2) Ashdown forest, through _______ we’ll be driving, isn’t a forest any longer.
A. that                                   B. it
C. them                                 D. which
(3) This I did at nine o’clock, after _______ I sat reading the paper.
A. that                                  B. it
C. them                                D. which
类似地，以下各题选 whom，不选 them：
(4) George, with _______ I played tennis on Sundays, was a warm-hearted person.
A. that                                   B. him
C. them                                 D. whom
(5) Her sons, both of ______ work abroad, will come back home this summer.
A. that                                  B. who
C. them                                D. whom
(6) I met the fruit-pickers, several of _______ were still university students.
A. that                                  B. who
C. them                                D. whom
■ He had thousands of students, many of ______ gained great success in their own field.
A. whom                               B. them
C. which                               D. who
【易错】容易误选 B，用 them 代指 students。
【分析】最佳答案是A，many of whom gained great success in their own field 为非限制性定语从句。假若在many of… 的前面加上连词and，则选答案B。比较以下各题(答案均选A)：
(1) He asked a lot of questions, none of ______ was easy to answer.
A. which                                 B. them
C. what                                   D. that
(2) He asked a lot of questions, and none of ______ was easy to answer.
A. them                                   B. which
C. what                                   D. that
(3) He told me that he had two girl-friends, neither of _______ knew anything about the other.
A. whom                                B. them
C. which                                D. who
(4) He told me that he had two girl-friends, and neither of _______ knew anything about the other.
A. them                                 B. whom
C. which                               D. who
■ He had a lot of friends, only a few of ______ invited to his wedding.
A. whom                               B. them
C. which                               D. who
【易错】容易误选 A，认为这是非限制性定语从句。
【分析】最佳答案是B，这不是非限制性定语从句，而是一个独立主格结构，因为空格后的动词 invited 并不是一个完整的谓语，而是一个过去分词。当然，假若在 invited 前加上助动词 were，则是一个非限制性定语从句，答案便应选A。比较：
(1) They put forward a lot of plans at the meeting, none of _______ carried out in their work.
A. which                                B. them
C. what                                  D. that
答案选B，none of them carried out in their work 是独立主格结构，其中的 carried out 为过去分词。
(2) They put forward a lot of plans at the meeting, none of _______ were carried out in their work.