目前，我国中央政府直接管理的价格为（）余种（类）。
A.10
B.20
C.30
D.40
参考答案：A
.The girl began to _____the piano when she was young.
A．practise to play
B．practise playing
C．practise to be played
D．practise play
对超声波气体流量计温度变送器的安装有何要求？
