单项选择题 When a point rotates about an axis and, at the same time, moves parallel to that axis, it describes （）.

单项选择题 An emergency bilge pumping system is provided and should be （） of the main bilge pumping system, according to the SOLAS 74 Convention.

单项选择题 The fire pumps must be capable of delivering a total quantity of water at a defined head, not less than （） of the total bilge pumping capacity.