二、单项选择（满分5分，共10题，每题0.5分）
16. No student is allowed to enter the lab without the teacher’s __________because some chemicals are dangerous to people.
A．permission B．protection C．preparation D．prevention
17. I will always remember the days ______I spent with my classmates.
A. that B. when C. on which D where
18. The computer is absolutely ______ amazing technological revolution. Just imagine what ______ fun it is communicating with people all over the world!
A. the; the B. an; 不填 C. 不填；a D. an; a
19. The day that I have been ____________________comes at last and I feel so excited that I can’t even sleep at night.
