圆水准器轴是圆水准器内壁圆弧零点的( )。
A．切线
B．法线
C．垂线
D．水平线
参考答案：B
I hope that you _____ a great time this evening. [ ]
A. have
B. will have
C. are having
D. had
B21-1型冷藏车的换长为（）。
A.2.1
B.2.0
C.1.8
D.1.7
