问一题，请教thus用法

genius1824

16. Migraine, the most debilitating common form of headache, afflicts perhaps 18 million Americans, who collectively lose 64 million workdays a year, and they cost the nation $50 billion in medical expenses and lost work time.

(A) year, and they cost the nation $50 billion in medical expenses and lost
(B) year and thus cost the nation $50 billion in medical expenses and lost
(C) year, so as to cost the nation $50 billion in medical expenses and lost
(D) year that costs the nation $50 billion in lost medical expenses and
(E) year, which thus cost the nation $50 billion in lost medical expenses and请问thus是否可指代前面一句话的内容，那么其后的谓语动词用单数还是复数？而且这道题中，cost为何不用costs呢?

finnlijing

thus一般与and连用,表因果关系,而这里lose and thus cost两个V并列做who的谓语,因为who指代americans,所以用复数

genius1824

谢谢

我还以为thus指代前面的那件事情呢。。。不过，americans cost...可以这

样说马？

finnlijing

我觉得,cost是不可以用人做主语的,是因为没有sb costs +钱的用法
但有sth costs sb +钱的用法
所以这里应该是可以这么用的吧,也就是没把美国人当人看???

kobemvp

cost 的主语是“Migraine",在migraine之后的“the most debilitating common form of headache, afflicts perhaps 18 million Americans" 都是插入语，修饰migraine的。

87338618

但是最后一句是修饰americans的啊，and的并列也是和who后面的内容并列，所以是americans， 我觉得。。

sarah_kims

那么为什么cost后面没有“S”？？我觉得cost的主语还是americans