轨道由道床、轨枕、钢轨、联结零件、防爬设备及道岔六部分构成。
参考答案：对
汽车进站关闭发动机做匀减速直线运动，当滑行x1=30m时，速度恰好减为初速度的一半，接着又滑行了t2=20s才停止。求：汽车关闭发动机时的速度v0和滑行的总时间t。
We went to the West Lake yesterday, _______, not surprisingly, was crowded with visitors from all
over the world. [ ]
A. where
B. which
C. that
D. when
