human-created aerosols interact.

　　Many parts of the world, in addition to China, are now suffering from increased levels of air pollution and understanding how dust, winds and emissions work together may help limit some of the worst impacts of dirty air.

　　One of the key lessons from this study is that the absence of dusty conditions could mean the air you are breathing is worse for you, not better.

3. According to the new study, the formation of air pollution over heavily populated parts of China is due to ________.

A. the accumulation of dust B. the lack of temperature

C. the high level of living standards D. the shortage of wind

4. What's the right sequence of cause and effect leading to the air pollution?

①the worse circulation of the winds

②more heat from the sun

③lessening temperature between the land and the sea

④less dust

⑤a worse stagnation

A. ④①③②⑤ B. ①④②⑤③

C.④②③①⑤ D. ①⑤②④③

5. What can be inferred from the passage?

A. Millions of people die of diseases caused by dirty air every year in China.

B. The theory of the consequences caused by declining Arctic sea ice is less scientific.

C. The new study must invite questions about how natural and human-created aerosols interact.

D. The absence of dusty conditions means a more healthier environment.

IT is fashionable to say that tech firms will conquer the financial services industry. Yet in the case of Apple, it seems that the opposite is happening and finance is taking over tech by stealth(悄然). Since the death of Steve Jobs, its co-founder, in 2011, the world's biggest firm by market value has sold hundreds of millions of phones with bionic chips (仿生芯片)and know-it-all digital assistants. But it has also grown a financial operation that is already, on some measures, roughly half the size of Goldman Sachs.

Apple does not organize its financial activities into one subsidiary, but Schumpeter has lumped them together. The result-call it "Apple Capital"-has $262bn of assets, $108bn of debt, and has traded $1.6trn of securities since 2011. It appears to be run fairly cautiously and is part of a thriving firm, but it still deserves scrutiny. Companies have a history of being hurt by their financial arms; think General Electric (GE) or General Motors (GM).

Apple Capital has lots of responsibilities but three stand out. It invests the firm's mountain of surplus profits, mainly in "highly rated" instruments (this task seems to fall to Braeburn Capital, a subsidiary in Nevada, which uses some external fund managers). Apple Capital also uses derivatives (衍生品)in order to protect the firm against currency and interest-rate gyrations. And it