我可以告诉你我的理解方法,where跟to(或其他介词） which是一样的都等于介词加the factory,所以排除. 如果要选where,应该是This is the factory where they worked 10 years.(work in the factory/这里where就等于in the factory) 这道题就是考你定语从句,that引导定语从句,修饰the factory,并且that在从句中做的visit的宾语.(记住:定语从句的引导词,如that,在从句中一定要做某个成分)B不能选,是where引导的是地点状语从句;C不能选,因为visit是及物动词,后边不需要加介词,否则就成了 visit to a place了.
