表盘直径不得小于（）毫米，精确度不低于2.5级。
A.50
B.100
C.120
D.150
参考答案：B
前序法是先访问 【4】 ，然后按前序周游左子树，按前序周游右子树。
Johnson would have faced the music but he ______ doing things like that.
A．had stopped
B．stopped
C．was stopping
D．has stopped
