单项选择题
A deepwell pump is a type of（）.
A.screw pump B.centrifugal pump C.eductor D.gear pump
单项选择题 A bowline is used to（）.
单项选择题 A block that can be opened at the hook or shackle end to receive a bight of the line is a（）.
单项选择题 You can safely step in the bight of a line（）.
