A．pressureB．speedC．levelD．flow

Compensated flow control or constant flow valves are used in hydraulic systems to .A.compe

【C5】A．displayB．activityC．actionD．flow

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

The word "duress" in Paragraph Two probably means______.A．pressureB．explanationC．persuasio

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

【C19】A．rateB．speedC．frequencyD．ratio