单项选择题
A.steam trap
B.check valve
C.separator
D.strainer
单项选择题 To maintain the down stream pressure within defined limits over a range of flow and despite any changes in supply pressure, （） is fitted.
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 （）.