引气剂与减水剂或高效减水剂等外加剂复配在同一水溶液中时，不得发生( )现象。
A．沉淀
B．絮凝
C．反应
D．冒气泡
参考答案：B
你注意到了吗？生活中，生物知识无处不在．图中的几则广告语，你认为符合生物学道理的是（ ）
A．
B．
C．
D．
August 8 was declared as National Fitness Day, when various events to encourage people to take more physical exercise.
A．held
B．were held
C．had held
D．have been held
