下列过程或现象与盐类水解无关的是 [ ]
A.纯碱溶液去油污
B.加热稀醋酸溶液其pH 稍有减小
C.小苏打溶液与AlCl3溶液混合产生气体和沉淀
D.浓的硫化钠溶液有臭味
答案:B
Most of the guests ______to his wedding are his close friends.
A.being invited
B.invited
C.inviting
D.had been invited
在关系中“主码”不允许取空值是指( )约束规则。
A.数完整性
B.用户定义的完整性
C.引用完整性
D.实体完整性