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【单选题】
对于压缩气体属于易燃易爆性质时，在启动往复式压缩机前，应该采用（）将缸内、管路和附属容器内的空气或其他非工作介质置换干净，并达到合格标准，杜绝爆炸和设备事故的发生。A.
氮气
B.
氧气
C.
水蒸气
D.
过热蒸汽
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知识点：
皮皮学刷刷变学霸
举一反三
【简答题】y'(t)＋2y’(t)＋2y(t)=f(t)，y(0_)=0，y’(0_)=1，f(t)=u(t)
【单选题】How can the companies cut their cost according to the passage?
A.
They dismiss some employees to save money.
B.
They use temporary labors and cheap labors.
C.
They don't pay for the employees' health insurance.
D.
They invest money on marketing campaigns.
【单选题】They can’t dismiss you just like that. They have to give you a written _____ first.
A.
example
B.
invitation
C.
warning
D.
requirement
【单选题】乙型肝炎病毒是威胁输血安全的主要病毒之一，原因是( )。
A.
乙肝病毒抵抗力强
B.
感染后造成肝脏损伤
C.
普通人群中乙肝感染率很高
D.
乙肝可以转化为肝硬化和肝癌
E.
乙肝病毒为DNA病毒
【单选题】How can the Companies cut their cost according to the passage?
A.
They dismiss some employees to save money.
B.
They use temporary labors and cheap labors.
C.
They refuse to pay for the employees' health insurance.
D.
They invest money on marketing campaigns.
【单选题】How can the companies cut their cost according to the passage?
A.
They dismiss some employees to save money.
B.
They use temporary labors and cheap labors.
C.
They refuse to pay for the employees' health insurance.
D.
They invest money on marketing campaigns.
【简答题】(由于惊奇、气愤或者激动)呼喊,惊叫
【简答题】记∇为差分算子,则下列不正确的是( )。 A 12-∇-∇=∇t t t Y Y Y B2122--+-=∇t t t t Y Y Y Y C k t t t k Y Y Y --=∇ D t t t t Y X Y X ∇+∇=+∇)
【简答题】完成对话。 A: _______ me, Bill. Can you _______ me? I can't find _______ pencil. B: Isn't it _______ your bag? A: No, it _______. B: Please look _______ it under the desk. A: Oh, it is over there. Thank yo...
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