捞油泵一般由连绳器、防打扭装置、中心管、（）、安全过载保护装置、加重悬挂装置等组成。
A、堵塞器
B、皮碗
C、密封圈
D、阀球
参考答案：B
John and his sister went on holiday with a cousin of _____. [ ]
A. his
B. her
C. their
D. theirs
_____________、_____________、______________构成了导游服务的三要素。
