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【单选题】
材料的()，是指材料在绝对密实状态下的体积与在自然状态下的体积之比。A.
表观密度
B.
密实度
C.
密度
D.
孔隙率
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【简答题】Part-time Front Desk Position, a book development company, is looking for a part-time front desk office worker. This position is very good for a person who is cheerful, dependable, and pleasant ...
【单选题】The teacher's desk is _____ the classroom. [ ]
A.
in front of
B.
in the front of
C.
in the front
D.
ahead
【多选题】在气门弹簧工作过程中,有时会发生共振现象,共振会使配气定时遭到破坏,使气门发生反跳和冲击,甚至是弹簧折断。为防止共振的发生,现代发动机中,采用了哪些结构措施避免气门弹簧的共振?
A.
采用双气门弹簧
B.
采用变螺距气门弹簧
C.
采用锥形气门弹簧
D.
采用气门弹簧振动阻尼器
【多选题】What are the standard duties of the Front Desk manager?
A.
Making sure the reservation cards are correctly filled, assigning rooms.
B.
Supervising all the Front Desk personnel.
C.
Scheduling the Front Desk staff.
D.
Assigning proper tasks based on various workloads.
【简答题】Part-time Front Desk Position , a book development company, is looking for a part-time front desk office worker. This position is perfect for a person who is cheerful, dependable, and pleasant to ...
【单选题】The teachers’desk is __________________ the classroom.
A.
behind
B.
in front
C.
in front of
D.
in the front of
【多选题】发动机气门弹簧的作用有哪些?
A.
保证气门弹簧可靠地工作。
B.
保证气门自动回位关闭而密封。
C.
保证气门与气门座的座合压力。
D.
吸收气门在开启和关闭过程中传动零件所产生的惯性力，以防止各种传动件彼此分离而破坏配气机构正常工作
【简答题】发动机气门弹簧的作用及要求有哪些？
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