单项选择题

The procedures recommended for auxiliary boilers having high salinity include （）.

A.treating with oxygen scavengers
B.securing the boiler and giving it a blowing down
C.increasing the pH
D.reducing the phosphate level

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单项选择题

Excessive alkalinity of the water in an auxiliary boiler can cause （）.

A.caustic embrittlement of the boiler metal
B.acidic corrosion of the boiler metal
C.hard scale deposits on the boiler tubes
D.etching of the heat exchange surfaces

单项选择题

The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.

A.assist in a quick cutoff of fuel injection
B.allow oil backflow from the injector to the helix
C.reduce fuel oil pressure between injection strokes
D.meter the quantity of fuel delivered