你选A可能是把Is this research center 想成了This is research center...所以后面缺宾语,选A.但是不应该这样变,应该是This research center is_______后面缺表语.所以应该加上先行词the one,在加上定语从句连词that...1)非常抱歉，应该用where 而不用that.把这个句子用两个陈述句写出来就是The research center is the one.(one 代替前面的research center）You visited the modern equipment in the research center last year. 这里visited是及物动词，modern equipment 是这个句子的宾语。两句变成一句，就用关系词连接起来。所以就变成了The research center is the one in which （代替the research center) you visited the modern equipment last year. 其中in which 又等于where 2）如果变成This is research center, 那么research center前缺少冠词。3）这句话的意思是，这是你们去年参观过的那个有现代设备的研究中心吗？ 个人意见，仅供参考！！