简述YJl7型卷烟机切烟刀片有效使用长度与进刀监测器设定值的关系。

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The last thirty years _____ the greatest number of laws stopping our rights and progress. Until today we have reached a stage _______ we have almost no rights at all．

A．saw; which

B．see; where

C．are seeing; in which

D．have seen; where

--- Would you like to go to the concert with me, Mary?

--- I have got no interest in it; ____, I have lots of homework to do.

A．otherwise

B．besides

C．however

D．therefore

加热炉风量过大时，火焰（）。

A、硬、发白

B、硬、发红

C、软、发白

D、软、发红

一般铜金属的电力设备接头过热后，其颜色会变得（）。

A.呈黑色

B.呈紫色

C.呈浅红色

D.呈灰白色

简述杀虫剂的定义。