1._____the first and largest ethnic group to work on the construction of the transcontiental railroad in the United Stat

1._____the first and largest ethnic group to work on the construction of the transcontiental railroad in the United States.
A.Chinese were B.The Chinese were C.Chinese was D.The Chinese were
2.A group of spectators was dispersed by the police who_____ at the scene of the accidents within minutes.
A.were B.have been C.was D.has been
给的答案是D A
B是The Chinese was
我认为第二题里面的who引导的句子是用来修饰警察的，但是为什么是单数，而不是复数呢？
修饰围观者么？句子的意思可以这样理解吧：一群围观者被几分钟之内就赶到事故现场的警察驱散开了。