a题 选B: that,因为先行词在句子中充当的是表语,所以只能用that而不能用which。
定语从句的引导词有关系代词who, whom,whose,which,that, as;关系副词when, where,why,所以what 一定是错的,至于用where 还是which/that,那要看这个定语从句的先行词在从句中充当的成分,这里的引导词充当的是visit的宾语,也就是说,能和visit组成一个动宾结构,即:visit the research center。而用where的场合,比如:
Please put the letter on the desk where he can easily find it.这个句子里先行词desk不能和find搭配。假如要用which,那要加上on,也就是where=on which:
Please put the letter on the desk on which he can easily find it.
先行词是物时,其引导词可用 which也可用that,通常情况下二者可互换,但在有些情况下不能。
1.用which不用that引导定语从句的三种情况:
①非限制性定语从句用which,不用that引导。
②先行词为that时,为了避免重复,定语从句用which不用that引导。
③介词后用which不用that引导。
2.用that不用which的七种情况:
①先行词前有形容词最高级或序数词修饰时,用 that不用which引导。
②先行词为little,much,all,none,few,(the)one, something,everything,nothing,anything等不定代词时,用that引导。
③先行词既有指人的名词又有指物的名词时,用 that引导。
④先行词前有any,all,no,few,every,some,little, much,(the)very,(the)only,(the)last等词修饰时,用 that引导。
⑤先行词为which时,为了避免重复,用that引导。
⑥先行词在从句中作表语时,常用that引导。
⑦当主句是There be...句型时,用that引导。
至于第二题,本来就不是一个定语从句。因为定语在句子中充当的作用,是对一个名词进一步的说明和限制,而假如一个名词是受到限制的,也就是说特指的,那一定要加定冠词the,所以不存在先行词不加定冠词的情况。 可作为表语从句来理解,用what 引导:
This research center is what you visited last year.
变成一般疑问句:Is this research center what you visited last year?
所以选A:what
五楼说得有道理啊,呵呵,我只考虑定语从句了。
温馨提示:答案为网友推荐,仅供参考