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

A．/; A

B．/; The

C．the; The

D．a; A

生物安全柜主要保护（）。

A.工作人员

B.检测样品

C.实验室仪器

D.实验室空气

E.A+B