杀毒软件的作用是杜绝病毒侵入计算机。( )

（13分）（1）对于下列反应：2SO₂ + O₂  2SO₃，如果2min内SO₂的浓度由6 mol/L下降为2 mol/L，那么，用SO₂浓度变化来表示的化学反应速率为____________，用O₂浓度变化来表示的反应速率为_____________。

（2）下图表示在密闭容器中反应：2SO₂+O₂2SO₃ △H<0 达到平衡时，由于条件改变而引起反应速度和化学平衡的变化情况。

①a b过程中改变的条件可能是        ；

②b c过程中改变的条件可能是           ；

③若加入催化剂，请将反应速度变化情况画在c~d处。

(3)请用化学平衡移动知识解释久置的氯水(尤其是长期放置在见光环境)，最后浅黄绿色消失，溶液变成稀盐酸:                                          

除去下列溶液中的杂质（括号内是杂质）所用试剂不正确的是[ ]

A．NaOH溶液[Ba(OH)₂]：用Na₂SO₄溶液

B．NaCl溶液(Na₂SO₄)：用Ba(NO₃)₂溶液

C．KOH溶液(K₂CO₃)：用Ca(OH)₂溶液

D．HNO₃溶液(HCl)：用AgNO₃溶液

Declaring that physical exercise is one of the most powerful medicines to help improve our quality of life is not an exaggeration. The World Health Organization expressed the same view in its 2002 World Health Report, emphasizing that the damage produced by lack of physical activity was equal to the p probability of serious illness such as heart disease and even some kinds of cancer.

Those who have embraced an active lifestyle for years are familiar with the sort of physical and psychological benefits that come from exercise. Nevertheless a lot of people would never think of physical activity as a way of feeling better, simply because they don’t think they are in need of it, or because they are lazy or maintain that they haven’t got enough time.

There are many positive effects that result from physical exercise and they are not only concerned with the physical aspects but also psychological and social ones.

Beginning with the physical benefits, physical activity improves the life of the heart, burns off fat, lowers high blood pressure, makes tissues more resistant, and increases muscle flexibility and joint mobility.

On a psychological level, physical activity helps reduce anxiety and stress by causing tension to disappear and by encouraging us to have a better sense of ourselves through listening to our bodies during movement.

Lastly, seeing ourselves in better health is advantageous socially. The sense of satisfaction thus obtained will result in an increase of self-respect and self-confidence in terms of our ability to interact with others.

The benefits linked to exercise have also not gone unnoticed in the business world, with more and more companies setting up gyms on-site. Employees’ improved health translates into better performance and reduced costs as well as an increase in people’s satisfaction in the work place.

Physical activity is recommended for all age groups, including children. It is an important growth factor in a child’s education.

And for the elderly There is no doubt that regular physical activity allows greater efficiency in daily life as well as creating more basic independence day by day, including the possibility of keeping in touch with others and not feeling isolated.

Many people do not engage in physical exercise mainly because ().

A. they are not aware of its benefits

B. they don’t have the facilities

C. they don’t think they need it

D. they are physically unfit for it

氧化锆氧分析器的测量值与锆头的温度（）.

A.成非线性

B.无关

C.成正比

D.成反比

指标评价法作为清洁生产评价的方法之一，如果没有标准可参考，可与国内外( )清洁生产指标作比较。

A．同类产品

B．同类装置

C．相同产品

D．以上都不是