题目

Topping the class academically was certainly an advantage. Studying was a breeze for Nigel. The reward was certainly incomparable to the little effort that he had to put it. It begin when he was selected to help the teachers in the computer laboratories. The peak of his school career came not when he topped the school but when he was selected for the nationwide competition. Unlike everyone else, Nigel wanted to join the contest because he liked playing with the Lego sets and making something out of them. Nigel spent the next two months rebuilding the robot. It was during the time that Nigel f浓度均为0.1mol/L的(NH4)2SO4、NaOH、NaHSO4、Na2SO4溶液，分别从25℃升到 95℃，其中pH值变化不大的是（物质的蒸发及溶液的体积变化忽略）                         （    ） A．(NH4)2SO4                  B．NaOH         C．NaHSO4        D．Na2SO4