问题
单项选择题
The backup system on an electric start survival craft is a（）.
A.hydraulic system
B.pneumatic system
C.spare battery
D.hand crank
答案
参考答案：D
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The backup system on an electric start survival craft is a（）.
A.hydraulic system
B.pneumatic system
C.spare battery
D.hand crank
参考答案：D