The five rings ____________the close unity and friendly meeting at the Olympics between athletes from five continents.

A．prove

B．represent

C．defeat

D．explain

膜片式汽油泵供油压力过高的原因是（）

A、油道有堵塞物

B、泵膜弹簧过软

C、摇臂无自由行程

D、泵麽弹簧过硬行程太长