广泛的深静脉血栓形成最严重的并发症是

A．腔静脉阻塞

B．肺栓塞

C．下肢坏疽

D．下肢溃疡

E．下肢浅静脉曲张

Which statement is TRUE concerning spare charges for portable fire extinguishers on unmanned tank barges?（）.

A.Spare charges shall be carried for at least 50 percent of each size and variety required on board

B.If the unit cannot be charged by the vessel's personnel，one spare unit shall be carried in lieu of spare charges

C.Spare charges shall be stowed in watertight containers on deck

D.Regulations concerning spare charges do not apply to unmanned barges