I had my bike this morning. [ ]
A. repair
B. repaired
C.repairing
D. repairs
答案:B
抬轿式扣轨铺设时先在路肩适当位置上搭设()枕木垛。
A、四个
B、六个
C、八个
D、十个
简述一般传动齿轮的设计方法和步骤。