- 搜標(biāo)題
- 搜題干
- 搜選項
單項選擇題
In using reduction gears to obtain efficient propeller speeds, （）.
A.they must be located at the after end of the engine
B.they can only be used with one engine at a time
C.they eliminate the need for controllable pitch propellers
D.they are connected to the engine with a flexible coupling
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