【C19】A．rateB．speedC．frequencyD．ratio

A．pressureB．speedC．levelD．flow

【28】A．variationB．balanceC．frequencyD．stability

Propeller running at ____ are generally efficient.A.high speedsB.medium speedC.low speedsD

____________ 查看材料A.rateB.motionC.systemD.disease

The government must increase the______of reforms to avoid further bloodshed.A．rateB．paceC．

Many people complain of the rapid______of modem life.A．rateB．speedC．paceD．growth