橡胶的加工指由生胶及其配合剂经过一系列化学与物理作用制成橡胶_爱下问搜题

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问题单项选择题

橡胶的加工指由生胶及其配合剂经过一系列化学与物理作用制成橡胶制品的过程：生胶的塑炼、塑炼胶与各种配合剂的混炼及成型、•胶料的（）等。

A、硫化

B、分解

C、氧化

D、促进

答案

参考答案：A

阅读理解

A Simple Scientific Experiment

Below is a description of a single scientific experiment. It shows us how iron reacts ( 反应) with air and with water.
Aim : To find out if iron rusts( 生锈) (a) in dry air ; (b) in water that has no air in it ( air- free water) ; (c) in ordinary water.
Materials : 3 clean iron nails ( 铁钉) ; test tubes ; test tube holder ; cotton wool ; oil ; Bunsen burner.

Iron in dry air
Method
(1)Put some iron nails at the bottom of a test tube.
(2)Push some cotton wool down the tube.
(3)Leave the tube for one week.
Result
After one week, the nails have not rusted.
Conclusion
Iron does not rust in dry air.
Iron in air-free water
Method
(1)Half-fill a test tube with water.
(2)Boil the water for three minutes. (This makes sure there is no air in the water.
(3)Put two or three clean nails in the water.

(4)Add some oil to the water. (This will keep air out of the water.)
(5) Leave the tube for one week.
Result
The nails do not rust in the tube with air-free water.
Conclusion
Iron does not rust in air- free water.
Iron in ordinary water
Method
(1)Half –fill a test tube with water and add two or three clean nails.
(2)Leave the tube for one week.
Result
The nails rust in the tube with ordinary water.
Conclusion
Iron rusts in ordinary water. (238 words)

小题1:In the first part of the experiment the cotton wool is most probably used to ______________.

A．keep the air dry	B．keep the tube wet
C．make the nails rust	D．keep the tube clean

小题2:What are necessary steps to make sure the water in the tube is air free?
①Leave half a tube of water in it
②Boil the water for some time
③Put some clean iron nails in the tube
④Add some oil to the water

小题3:We can conclude from the experiment that only ____________ makes iron rusty.

B．cotton wool

C．ordinary water

D．air-free water

单项选择题

某股份有限公司对期末存货采用成本与可变现净值孰低法计价，2004年12月31日A库存商品的实际成本为40万元，预计进一步加工所需费用为16万元，预计销售费用及税金为8万元。该库存商品的市场销售价格为60万元。假定该公司以前年度未计提存货跌价准备，则2004年12月31日该项存货应计提的跌价准备为( )万元。

A．0

B．4

C．16

D．20