能全部通过二号筛，但混有能通过四号筛不超过40%的粉末（）
A．最粗粉
B．粗粉
C．细粉
D．最细粉
E．极细粉
参考答案：B
Not only his parents but also his brother to the Summer Palace. They will be back next week.
A．have been
B．have gone
C．has gone
D．has been
请问浅水波是（）。
A．波长远小于海深的波
B．波长远大于海深的波
C．波长等于海深的波
D．水深小于10m说出现的波
