在()秒内未触摸任何键盘时,激光测距仪就会自动关机。
参考答案:90
We are doing _____. [ ]
A. our homework
B. my homework
C. one's homework
D. homeworks
溢油阀装在冷油器进口油路管道上,其作用是保持润滑油压稳定。()