题目

He is so stubborn that once he makes up his mind, nothing can change it, _______, it's no use arguing with him. A . therefore B . however C . besides D . so 答案：ANH4+离子浓度相同的下列各物质的溶液中，物质的量浓度最大的是A.NH4Al(SO4)2B.NH4HCO3C.NH4HSO4D.NH4NO3