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【单选题】
The "Helios" UAV of the United States have ____ propellers.
A.
10
B.
12
C.
14
D.
16
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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【多选题】The power source of electric power device mainly comes from: ____.
A.
Solar cell
B.
Battery
C.
Wind energy battery
D.
Fuel cell
【单选题】The thrust-to-weight ratio of rocket engines could reaches ____.
A.
30-40
B.
50-70
C.
80-120
D.
100-150
【多选题】The advantages of rocket engine compared with aeroengine include: ____.
A.
The thrust is not affected by the flight attitude
B.
Larger thrust
C.
High thrust-to-weight ratio
D.
Self-contained combustion agent