Dr. Peter Spence, ____ headmaster of the school, told us, “____ fifth of pupils here go to study at Oxford and Cambridge.”

A．a; A

B．不填；The

C．the; The

D．不填; A

某校环保小组监测到一个造纸厂仍向淮河排放无色碱性污水，请你根据所学知识，设计两个实验来证明：

（1）___________________________________________；

（2）___________________________________________。