单项选择题
Atmospheres laden with coal dust or grain dust caused by loading these cargoes（）.
A.require loading operations to be shut down until the atmosphere clears B.are toxic to human life C.are subject to spontaneous combustion D.may be explosive in some concentrations
单项选择题 A venetian vent or rice ventilator is used in stowage of which cargo?（）.
单项选择题 A grapnel is a（）.
单项选择题 A deck beam does NOT（）.
