正确答案: C

螺杆单头，衬套双头

题目：单螺杆泵螺杆和衬套的螺纹头数( )。

解析：C

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举一反三的答案和解析：

[单选题]关于紧急脱险呼吸装置（EEBD），下述说法错误的是______。

未启用的紧急脱险呼吸装置应用手才能携带

[单选题]One of the reasons that causes oil flowed from sludge outlet of a self-cleaning purifier is

make-up water supply be cut off

[单选题]Where ________ you ________?

have/been

[单选题]Which of the following is operated from the main engine room console on an automated vessel?

Fire pump and lube oil pump

[单选题]右肩关节脱位可出现______。

右肩胛盂空虚

[单选题]机器处所所要求的固定式高倍泡沫灭火系统应能通过固定喷射口迅速喷出泡沫，其数量足以_______min向被保护处所中的最大者至少注入1m深的泡沫。

1

[单选题]In the Second paragraph, the underline word "Who", in such a context, stands for_____.

the Administration, the recognized organization or the nominated surveyor responsible for issuing the relevant Certificate

[单选题]前后两船处于追越过程中，发生下列哪种情况不可以免除追越船让路责任？I、前船已停车甚至倒车；II、前船突然显示搁浅信号；III、在狭水道中，前船已同意追越并采取行动；IV、前船不履行保向保速义务而转向

I、II、III、IV

[单选题]除客船外其他船舶的救生艇降落水面的时间不超过：

10分钟