单项选择题
High clouds，composed of small white flakes or scaly globular masses，and often banded together to form a “mackerel sky”，would be classified as（）.
A.cirrus B.cirrocumulus C.altostratus D.cumulonimbus
单项选择题 Hanging a barge off means to（）.
单项选择题 Handholds or straps on the underside of an inflatable liferaft are provided（）.
单项选择题 Halon fire extinguishers are NOT effective when used on which types of fires?（）
