单项选择题
A.a check valve
B.a gate valve
C.a pressure reducing valve
D.a quick closing valve
单项选择题 The main objective of the SOLAS Convention is to specify （） for the construction, equipment and operation of ships, compatible their safety.
单项选择题 Annex IV of MARPOL 73/78 contains regulations for the prevention of （）.
单项选择题 The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the （） of merchant ships.