我开始选的是A,但是后来想想,是不是这里B中cost主语是人,是一种形象的用法,因为那些得病的人要去看病(medical expenses)或请假 (lost work time),这些都cost the nation,所以就用了Americans cost the nation in medical expenses and lost work time,其结构跟 OG110 那句 illiteracy costs the United States at least $20 billion a year in lost industrial output and tax revenues 如出一辙,illiteracy导致了lost industrial output and tax revenues,这些都cost United States。