还原成为陈述句： This is the museum ____ the exhibition was held. the museum后接的是定语从句,如果要用that,句中应该缺少主语或宾语或表语,而the exhibition was held是完整的,所以得用关系副词where,相当于in which 如：Is this the book that you lent him?(从句中缺少宾语）就可以用that 再问： 能细说一遍吗，这俩个没有区别啊 再答： Is this the book （that you lent him本句定语从句lent him后面还要加一个宾语book，所以用that代替book）? Is this the museum (where the exhibition was held定语从句结构完整了).
