单项选择题
Starting motors，generators，and other spark producing devices should be mounted as high above the bilges as possible to（）.
A.keep them dry when the bilges are full of water B.keep them cool when the vessel is underway C.make them more accessible for repairs D.prevent accidental ignition of any gasoline vapors that may have accumulated in the bilges
单项选择题 Small hull leaks can be temporarily repaired by（）.
单项选择题 Rivets are usually made of（）.
单项选择题 Repairing damage to the hull at or above the waterline reduces the threat of（）.
