11.That is the most expensice hotel__Ihave stayed so far.
a.where b.that c.which d.what
有the most 出現，為什麽不選that？

12.I’m afraid this is the only restaurant in this town__ you can get such wonderful food.
a.that b.of which c.by which d.where
the only 出現為什麽不選that？

13.Is this research center___ you visited the modern equipment last year?
a.which b.that c.the one where d.the one that
research center不是先行詞嗎？

14.It was a shame that the famous painter should die his painting____
a.unfinished b.was unfinished c.being unfinished d.having unfinished
時態嗎？不懂得看。。

11、12理由完全相同：
先行词hotel、restaurant在定语从句都是做地点状语（stay at this hotel、get food in this restaurant），而非宾语或主语，所以只能用表示地点的关系副词。

13 research center不是先行词。要判断哪个单词或词组是先行词，你要先将句子还原成肯定句，由于research center前没有the，所以这个词组只能和this连用作为主语，否则就不符合英语中关于名词前冠词用法的语法规则了，还原的结果为：This research center is ____ you visited the modern equipment last year.这样一来，就能发现先行词必须只能是is后面的那个表语，即the one，关系代词因在从句作的是及物动词visit的宾语而要用that，或者干脆后半句不用定语从句而改用表语从句，这时关联词就要用what了。

14 A
这里考核的是独立主格结构，his painting是非谓语动词的逻辑主语，他和unfinish的关系是动宾关系，所以只能用过去分词，或者你可以把unfinished看成是形容词，当中省略不必要的谓语动词be。