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单项选择题

真空检漏：启动回收/净化/加注设备的真空泵，抽真空至系统真空度低于-90kPa。关闭歧管表阀门，停止抽真空，并保持真空度至少30min，检查压力表示值变化。                                                    （   ）

A．对
B．错
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单项选择题
大脑半球的外侧面大部分供血来自
A、大脑前动脉皮质支
B、前交通动脉
C、大脑中动脉中央支
D、大脑中动脉皮质支
E、脉络膜前动脉
未知题型
Pick out appropriate expressions from the eight choices below and complete the following write down the corresponding letter.
A.Ifs impossiblE.B.I suggest we go to the seasidE.
C.I'd like to tell you something. D.How about going to the art exhibition?
E.I hope not. F.We'd better think of something elsE.
G. I'm afraiD.H. I'm very sorry to hear that.
Tony: Do you have a plan for the coming holiday?
Lucy: Yes.【56】.
Tony: But what about it if the weather changes?
Lucy:【57】. Well, you're right.【58】.
Tony:【59】. It was said it is worth seeing.
Lucy: Good ideA.We ought to call Charlie before that. Otherwise he may go away. Do you think so?
Tony:【60】. Anyway, it would be better to let him know beforehanD.
(57)
单项选择题
离心泵启动时，泵内应充满输送的液体，否则会发生气缚现象。（ ）
A．对
B．错
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