向一定体积的饱和石灰水中加入少量生石灰，并恢复到原状况。则下列叙述正确的是
A：溶液的pH增大
B：溶液的pH减小
C：溶液中Ca2+浓度保持不变
D：溶液中Ca2+物质的量保持不变
下列观点符合质量守恒定律的是( )
I____ ____ ____ ____so I can help you．
—I think teenagers should be allowed to make their own decisions when they have problems at school.
—_______. They're not calm enough, after all.
