出境入境边防检查条例规定，边防检查站有权阻止出境、入境的情形有（）。 A.持用他人出

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“脑黄金”在医药、食品等行业中应用前景非常广阔，其主要成分是C₂₅H₅₁COOH （DHA），下列关于DHA的说法正确的是（　　）

A．DHA中碳、氢、氧元素质量比为13：26：1

B．DHA属于氧化物

C．VDHA分子是由碳、氢、氧三种元素组成的

D．DHA的每个分子是由80个原子构成的

滑雪是冬天一项极具刺激性的体育运动，如图甲所示，滑雪者踏着雪橇（它们的总质量为75kg）在倾角θ=37°的斜面上向下滑动，在运动过程中受到的空气阻力与速度成正比，现测得雪橇运动的v-t图象为乙所示，图中的AB直线是曲线的切线，B点坐标为（4，15），CD是曲线的渐近线，试求：

（1）雪橇开始做什么运动，最后做什么样的运动？

（2）当雪橇的速度为5m/s时，它的加速度为多大？

（3）空气的阻力系数k和雪橇与斜坡间的动摩擦因μ（g取10m/s²，sin37°=0.6）．

In 1880, Sir Joshua Waddilove, a Victorian philanthropist, founded Provident Financial to provide affordable loans to working-class families in and around Bradford, in northern England. This month his company, now one of Britain’s leading providers of "home credit"— small, short-term, unsecured loans—began the nationwide rollout of Vanquis, a credit card aimed at people that mainstream lenders shun. The card offers up to ￡ 200 ($ 380) of credit, at a price: for the riskiest customers, the annual interest rate will be 69%.

Provident says that the typical interest rate is closer to 50% and that it charges no fees for late payments or breaching credit limits. Still, that is triple the rate on regular credit cards and far above the 30% charged by store cards. And the Vanquis card is being launched just when Britain’s politicians and media are full of worry about soaring consumer debt. Last month, a man took his own life after running up debts of ￡ 130000 on 22 different credit cards.

Credit cards for "sub-prime" borrowers, as the industry delicately calls those with poor credit records, are new in Britain but have been common in America for a while. Lenders began issuing them when the prime market became saturated, prompting them to look for new sources of profit. Even in America, the sub-prime market has plenty of room for growth. David Robertson of the Nilson Report, a trade magazine, reckons that outstanding sub-prime credit-card debt accounts for only 3% of the $ 597 billion that Americans owe on plastic. The sub-prime sector grew by 7.9% last year, compared with only 2.6% for the industry as a whole.

You might wonder, though, how companies can make money from lending to customers they know to be bad risks—or at any rate, how they can do it legitimately. Whereas delinquencies in the credit-card industry as a whole are around 4%-5% , those in the sub-prime market are almost twice as high, and can reach 15% in hard times.

Obviously, issuers charge higher interest rates to compensate them for the higher risk of not being repaid. And all across the credit-card industry, the assessment and pricing of risks has been getting more and more refined, thanks largely to advances in technology and data processing. Companies also use sophisticated computer programs to track slower payment or other signs of increased risk. Sub-prime issuers pay as much attention to collecting debt as to managing risk; they impose extra charges, such as application fees; and they cap their potential losses by lending only small amounts ($ 500 is a typical credit limit).All this is easier to describe than to do, especially when the economy slows. After the bursting of the technology bubble in 2000, several sub-prime credit-card providers failed. Now there are only around 100, of which nine issue credit cards. Survivors such as Metris and Providian, two of the bigger sub-prime card companies, have become choosier about their customers’ credit histories. As the economy recovered, so did lenders’ fortunes. Fitch, a rating agency, says that the proportion of sub-prime credit-card borrowers who are more than 60 days in arrears (a good predictor of eventual default) is the lowest since November 2001. But with American interest rates rising again, some worry about another squeeze. As Fitch’s Michael Dean points out, sub-prime borrowers tend to have not just higher-rate credit cards, but dearer auto loans and variable-rate mortgages as well. That makes a risky business even riskier.

It can be inferred from the passage that（）

A. the failure of credit card providers is caused by the bursting of technology bubble

B. the politicians and the media play a negative part in promoting credit industry

C. higher national interest rate increases sub-prime lenders’ risks of not being repaid

[D] credit industry has a better chance of development when the economy slows down

对热原的性质叙述正确的是

A．反渗透法不能除去热原

B．250℃ 30～45分钟可以彻底破坏热原

C．热原大小约在1～5nm之间，可以被微孔滤膜截留

D．热原能溶于水，超滤装置也不能将其除去

E．活性炭可以吸附色素与杂质，但不能吸附热原