转向架组成后，钢轨内侧各垂下品与轨面最小距离为（）
A.25mm
B.48mm
C.60mm
D.80mm
参考答案：C
Did you have a hard time _____ to Beijing? [ ]
A. get
B. got
C. to get
D. getting
简述普惠制的主要原则和目的？
