计算a3•a2的结果是（ ）
A．a6
B．a5
C．2a3
D．a
a3•a2=a3+2=a5．故选B．
—Whose schoolbag is this?
—It ___________ be Mary’s. It has her name on it.
A．can
B．may
C．will
D．must
时钟共12格，每格度数为______度，3时时针所转角度为______度．
