题型:单项选择题 有R和S表如下图所示,A是R的主键和S的外键,D是S的主键,且R与S实施了参照完整性。下列元组中可以正确插入S的是( ) [*] A.(a1,d1,45) B.(a2,d2,34) C.(a3,d5,null) D.(a3,null,21) 查看答案
题型:选择题 The traffic problem we are looking forward to seeing ____ should have attracted the localgovernment's attention. [ ]A. solving B. solved C. to solve D. solve 查看答案