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單項(xiàng)選擇題

A device fitted over the discharge opening on a relief valve consisting of one or two woven wire fabrics is called a（）.

A.flame stopper
B.flame screen
C.flame filter
D.flame restrictor

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單項(xiàng)選擇題

A device used to enlarge the size of an existing bore hole, having teeth arranged on its outside circumference to cut the formation as it rotates is a (n)（）.

A.enlarge bit
B.casing bit
C.hole opener
D.casing opener

單項(xiàng)選擇題

A Doppler log in the bottom return mode indicates the（）.

A.velocity of the current
B.bottom characteristics
C.depth of the water
D.speed over the ground

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