题目

—My plane is the one that at 10 a.m.—Then you need to hurry. It in half an hour. A . is about to take off, takes off B . is about to take off, is taking off C . takes off, is taking off D . takes off, is about to take off 答案：C10．在一定条件下，同一反应进行的快慢与反应物的溶质质量分数成正比．现在用100克溶质质量分数为30%的硫酸溶液与过量的镁粉反应，为了使反应慢点而又不影响生成氢气的总量，可以向该硫酸溶液中加入适量的（　　）A．氢氧化钠B．硫酸钾溶液C．碳酸钠溶液D．碱式碳酸铜