1,This is the school _____I visited last summer
A.where B.who C.which
注：可以把句子倒过来换成陈述句：I visited the school last summer,可以看出这里the school是做宾语,可以用which和that ,所以选C
2、This is the school ____I studied ten years ago
A.where B.that C.which
注：同上,换成陈述句：I studied in this school ten years ago.
the school 做状语,school后可以跟 in which（in是搭配school） 和 where ,C选项漏了介词in,故选A