In more recent years, （） heat exchangers have frequently been employed for jacket water and oil cooling.

To avoid impingement attack, care must be taken with the water （） through the tubes of the heat exchangers.

A.temperature
B.velocity
C.density
D.viscosity

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A non-return valve in the air delivery line near to the compressor must be （）type similar to the compressor discharge valve.

A.the low inertia
B.the high inertia
C.the low velocity
D.the high velocity

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