单项选择题 If the action of the engine indicates that some of the cylinders are not firing, the ones affected may be determined by watching （）.

单项选择题 The injection may be delayed, （）the pumps are in good order, if the fuel lines to the injection valves have not been cleared of air.

单项选择题 If cylinder liner wear is up to maximum limits the possibility of scavenge fires will not be materially reduced until the liners are （）.