中学阶段是人的心理、生理的[ ]
A、关键时刻
B、初级阶段
C、最终阶段
D、最高时期
答案：A
订算题.
1. What number should replace the question mark?
Answer:________________________________________________________
2. Eric is five years younger than his sister. Five years ago, his age was l/6 0f his sister.
how old is Eric now?
Answer:_________________________________________________________
下列物体中属于导体的是（）
A.陶瓷
B.硅
C.硒
D.石墨
