交互式教学模式是由教师与小组学生一起进行的，这小组学生人数最好在（）
A.3人左右
B.6人左右
C.10人左右
D.13人左右
参考答案：B
染色体的主要成分是[ ]
A．蛋白质和DNA
B．基因与DNA
C．只有蛋白质
D．只有DNA
— I'm sorry. I _____ at you the other day.
— Forget it. I was a bit out of control myself.
A. shouldn't shout
B. shouldn't have shouted
C. mustn't shout
C. mustn't have shouted
