单项选择题
A.bottom B.middle C.top D.none of the above
Aluminum pistons have （） coefficient of thermal expansi...
单项选择题Aluminum pistons have （） coefficient of thermal expansion compared with those of cast iron.
A.higher B.lower C.the same D.none of the above
Although the crankshafts of medium diesel engines appea...
单项选择题Although the crankshafts of medium diesel engines appear to be robust, they rely on the support of （） to develop their full strength.
A.the piston rods B.the crank throws C.the thrust bearings D.the main bearings
All three systems have the ports （） to swirl the incomi...
单项选择题All three systems have the ports （） to swirl the incoming air and direct it in the appropriate path.
A.angled B.rounded C.being angled D.being rounded
