The buses, were already full, were surrounded by an angry crowd.
A. most of them
B. which most
C. most of which
D. that most
网友回答
A. most of them
B. which most
(答案→)C. most of which
D. that most
解析：考查非限制性定语从句。根据逗号判断，句子是非限制性定语从句，most of...意为“......的大多数”，排除B、D；A项不能引导从句，如果在逗号后添加and，则句子变成两个并列的分句。目前来看，句子是主从复合句，most of which指代大多数公交车，故选C。