Any increase in the exhaust back pressure of a four－stroke／cycle diesel enginewill( ).

Any increase in the exhaust back pressure of a four-stroke/cycle diesel enginewill( ).

A.reduce engine horsepower output

B.aid in silencing the exhaust noise

C.increase the mean effective pressure

D.contribute to effective cylinder scavenging

A解析：aid：援助;contribute to：对…起作用译文：四冲程柴油机排气背压升高将会减少发动机的功率输出。