困扰很久的一种选择题类型Is this research center ____ the foreign guests

答案为D
把这句话变为肯定句就是
this research center is____ the foreign guests visited last week.
注意：不能变为
this is research center ____ the foreign guests visited last week?
因为is和research center之间没有冠词the,答案E就错在这里,因为这句句子不是泛指,是具体的指“this research center”
所以原句为
this research center is the one （which） the foreign guests visited last week.
在这里the one指代research center,而当which指代的事物(这里是research center)为定语从句的宾语时,可以省略.所以这里which倍省略了.

the是重点强调的,后者不是,可以随便点的

c后面没有地点，所以用where

D.这是定语从句的一种特殊类型.它的解法就是把主句还原为一个陈述句,this research centre is_____这里主句缺少的是表语,而后边是一个定语从句,所以,相当于特指,必须有定冠词the,又如,Is this house the one you repaired yesterday?