问题
选择题
Is this research center ________ you visited the modern equipment last year?
A．where
B．that
C．the one that
D．the one where
答案
答案：D
将疑问句改为陈述句：this research center is…显然缺少先行词，必须加上代词the one来作先行词，又因定语从句不缺主语或宾语，所以用关系副词where。假若在this后加the，就选where，请想想这是为什么。