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问题 多项选择题

下列描述安全阀工作原理的说法正确的是（）。

A、安全阀通常受弹簧作用或导阀控制

B、安全阀有杠杆式和弹簧式等类型

C、当入口处静压超过设定压力时，阀瓣上升以泄放被保护系统的超压

D、当压力将至回座压力时，则自动关闭

答案

参考答案：A, B, D

单项选择题

双波纹管差压计记录笔在记录纸分度线上自终端移动所划的弧线与时间线的偏差应不大于（）。

A.0.3mm

B.0.4mm

C.0.5mm

D.0.6mm
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单项选择题

Last year the worldwide paper industry used over twice as much fresh pulp (pulp made directly from raw plant fibers) as recycled pulp (pulp made from wastepaper). A paper-industry analyst has projected that by 2010 the industry will use at least as much recycled pulp annually as it does fresh pulp, while using a greater quantity of fresh pulp than it did last year.
If the information above is correct and the analyst’s projections prove to be accurate, which of the following projections must also be accurate

A．In 2010 the paper industry will use at least twice as much recycled pulp as it did last years.

B．In 2010 the paper industry will use at least twice as much total pulp as it did last year.

C．In 2010 the paper industry will produce more paper from a given amount of pulp than it did last year.

D．As compared with last year, in 2010 the paper industry will make more paper that contains only recycled pulp.

E．(E) As compared with last year, in 2010 the paper industry will make less paper that contains only fresh pulp.
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