轮对
参考答案：
由两个车轮紧密地压装在一根车轴上组成的，轮对承受车辆的全部重量，并以较高的速度引导车辆在钢轨上行驶
—A girl called Lucy wants to see you outside.
—Are you sure? _____ I'm new here. No one knows me in this city. [ ]
A. And
B. if
C. But
D. So
