病例对照研究中最常见的偏倚有（）。 A.回忆偏性 B.选择偏性 C.调查员偏性 D.

生活饮用水水 质的标准主要有：色度、混浊度、pH、细菌总数、嗅和味等等。目前城市自来水处理过程中所使用的主要药剂仍是Cl₂（消毒剂）和Al₂(SO₄)₃（沉降剂），但由于种种原因，用这两种物质处理水质，总有缺陷。因此,有资料报道：Na₂FeO₄是一种强氧化剂，可作为一种新型净水剂，在反应中被还原为Fe³⁺离子，使用该物质可代替Cl₂和Al₂(SO₄)₃

（1）配平工业上制备铁酸钠的化学方程式：

（2）当反应物中含有1.4mol钠离子，上述反应恰好完全进行时，电子转移总数为____N_A。

（3）Na₂FeO₄代替Cl₂是因为它具有__________性，还原为Fe³⁺后净水的原理为（用离子方程式表示）_________

（4）某厂制备铁酸钠后的废液中含NaNO₂溶液，直接排放会造成污染，下列试剂中

①NaCl ②NH₄Cl ③KMnO₄ ④浓H₂SO₄，能使NaNO₂转化为N₂（不引起二次污染的）是______(选填编号)，反应离子方程式___________________________

In today’s world, almost everyone knows that air pollution and water pollution are harmful to people’s health. However, not all know that noise is also a kind of pollution, and that is harmful to human, too.

People who work and live under noisy conditions usually become deaf(耳聋的). Today, however, scientists believe that 10% of workers in Britain are deafened by the noise where they work. Many of the workers who print newspapers and books, and who weave cloth become deaf. Quite a few people living near airports also become deaf. Recently it was discovered that many teenagers in America could hear no better than 65-year-old people, for these young people like to listen to “pop” music and most of “pop” music is a kind of noise. Besides, noise produced by jet plane or machines will make people’s life difficult and unpleasant, or even make people ill or even drive them mad. It is said that a continuous noise of over 85 decibels（分贝） can cause deafness.

Nowadays the governments in many countries have made laws to reduce or control noise and make it less than 85 decibels. In China, the people’s government is trying to solve not only air and water pollution problems but also the noise pollution problems.

小题1:In the world today, not every person knows        .

A．water pollution

B．air pollution

C．harmful pollution

D．noise pollution小题2:Today scientists believe that       .

A．90% of all the workers in Britain are not suffering from noise

B．10% of all the workers in Britain are working in noisy places

C．10% of all the workers in Britain are deafened by the noise where they work.

D．90% of all the workers are free from any noise小题3:Those who       usually have poorer hearing.

A．weave cloth

B．sell newspapers

C．like listening to music

D．often travel by plane小题4:According to the passage, a continuous noise       can make you deaf.

A．in working places

B．of less then 85 decibels

C．of over 85 decibels

D．of only 85 decibels

通货膨胀时期，所有价格和工资都按同一比率变动，每个人的收入和财富都得到增加。( )

版样上如果有（）外的其他文字，应请专业人员翻译核对。

A.汉语

B.英语

C.拼音

D.印刷

调节冷却水泵跳停不会影响中和温度。