Before welding is permitted on a fuel tank, it must be certified or declared .
A.safe for becoming rounded
B.safe for hot work
C.not safe for personnel
D.not safe for hot work
第1题
A.the S.W outboard valves
B.the tailshaft L.O stop valve
C.the drain valve of the boiler
D.propeller shaft sealing device
第2题
A.make use of
B.have made the use of
C.by means of
D.make advantage of
第3题
A.specific gravity
B.viscosity
C.acid value
D.calorific value
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