单项选择题
A.lighter than air B.heavier than air C.a yellow gas that is easily recognized D.mildly toxic
A.respiratory irritant B.skin burning agent C.blood poisoning agent D.nerve paralyzing irritant
A.separating cargoes so that the inherent characteristics of one cannot damage the other B.separating cargoes by destination C.classifying cargoes according to their toxicity D.listing the cargoes in order of their flammability