單項(xiàng)選擇題A time diagram is a diagram of the celestial sphere as observed from above the（）.

A.south celestial pole
B.north celestial pole
C.observer's meridian
D.Greenwich meridian


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1.單項(xiàng)選擇題A thrust block is designed to（）.

A.transmit the thrust of the engine to the propeller
B.transmit the thrust of the propeller to the vessel
C.absorb the shock of wave pressure at the bow
D.be placed between the engines and the foundation to absorb the vibration

2.單項(xiàng)選擇題A thin，whitish，high cloud popularly known as “mares’ tails” is（）.

A.altostratus
B.stratus
C.cumulus
D.cirrus

3.單項(xiàng)選擇題A tank 36 ft. by 36 ft. by 6 ft. is filled with water to a depth of 5 ft. If a bulkhead is placed in the center of the tank running fore-and-aft along the 36-foot axis，how will the value of the moment of inertia of the free surface be affected?（）

A.The moment of inertia would remain unchanged
B.The moment of inertia would be 1/4 its original value
C.The moment of inertia would be 1/2 the original value
D.None of the above

4.單項(xiàng)選擇題A tackle is “two blocked” when the blocks are（）.

A.equally sharing the load
B.jammed together
C.as far apart as possible
D.rove to the highest mechanical advantage