单项选择题
The exhaust gases for a new engine should be （） when the engine operates under full load.
A.smoky B.a little bit dense C.visible D.almost invisible
单项选择题 The engine will fail to start unless （）.
单项选择题 “The engine not obtaining the sufficient speed for firing” means that （）.
单项选择题 The engine may lose power or slow down during running, when this occurs, the first cause possible may be hot bearings and （） of the pistons in the cylinders.
