单项选择题
Halon fire extinguishers are NOT effective when used on which types of fires?（）
A.Fires in electrical equipment B.Flammable oils and greases C.Class "A" fires in ordinary combustibles D.Materials containing their own oxygen
单项选择题 Guide tolerances during elevation of the jack-up rig will（）.
单项选择题 Great Salt Pond on Block Island is（）.
单项选择题 Good seamanship while towing in heavy weather requires all of the following EXCEPT（）.
