單項(xiàng)選擇題The minimum concentration of a vapor in air which can form an explosive mixture is called the（）.

A.auto-ignition point
B.flash point
C.lower explosive limit (LEL)
D.threshold limit value (TLV)


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1.單項(xiàng)選擇題The minimum amount of lifesaving equipment required aboard an 85-foot uninspected towing vessel consists of（）.

A.one approved flotation cushion for each person on board
B.one approved life preserver for each person on board and one life ring
C.one approved inflatable vest for each person on board
D.lifeboat capacity equal to 1 1/2 times the number of persons on board

2.單項(xiàng)選擇題The MINIMUM acceptable size for a towing bridle would be that size in which the safe working load (SWL) of each leg of the bridle is equal to（）.

A.one-half the SWL of the main towing hawser
B.three-fourths the SWL of the main towing hawser
C.that of the main towing hawser
D.twice that of the main towing hawser

3.單項(xiàng)選擇題The maximum speed of lowering for a lifeboat on gravity davits is controlled by the（）.

A.limit switches
B.emergency disconnect switch
C.governor brake
D.position of the counterweight on the brake handle

4.單項(xiàng)選擇題The Master or person in charge of a ship shall insure that each deck from which lifeboats are launched is（）.

A.surfaced with a nonskid texture
B.roped off to prevent unnecessary access
C.kept clear of any obstructions that would interfere with launching
D.posted with a list of persons assigned to the lifeboat

5.單項(xiàng)選擇題The lifeboat releasing gear lever should be marked with the words（）.

A.DANGER，DO NOT TOUCH
B.DANGER，BOAT MAY DROP
C.DANGER，LEVER RELEASES BOAT
D.DANGER，LEVER DROPS BOAT