问题补充:
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:
A. where
B. that
C. the one that
(答案→)D. the one where
解析: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。