横过停有机车、车辆的线路时，如何通过较为安全？
参考答案：
应先确认该机车、车辆暂不移动，然后由该机车车辆较远处通过。
After ________in the research for so many years，the scientist succeeded in finding the result at last.
A．buried
B．being buried
C．having buried
D．having been buried
圆柱齿轮减速箱有单级、两级、三级的三种形式。
