单项选择题
A.Having adjusted B.Being adjusted C.To adjust D.Adjusted
The four-stroke cycle begins with the piston （）.A.comin...
单项选择题The four-stroke cycle begins with the piston （）.
A.coming up from the BDC B.coming up from the TDC C.coming down from the BDC D.coming down from the TDC
Pump up the starting air reservoirs to their maximum pr...
单项选择题Pump up the starting air reservoirs to their maximum pressure and （）the air reservoirs and air system.
A.open B.close C.drain D.vent
James Watt （）the steam engine in 1796.A.discoveredB.had...
单项选择题James Watt （）the steam engine in 1796.
A.discovered B.had discovered C.invented D.had invented
