所谓的硕士研究生入学考试是什么意思

在分子生物学领域中，分子克隆主要是指
A. DNA的大量复制 B. DNA的大量剪切
C. RNA的大量复制 D. RNA的大量转录

Text4 Most forecasts suggest that Britain will be a poorer country afier Brexit,largely because trading with the European Union will become more difficult.Such predictions about the distant future are,by their nature,open to doubt,which is partly why Brexit's proponents feel free to dismiss them.But the same does not apply to a new paper by Meredith Crowley,Oliver Exton and Lu Han from Cambridge University,which suggests that,months before Brexit has even happened,trade is already suffering,as firms respond to the prospect of higher tariffs.More than 100,000 British businesses export goods to the EU each year.At present they enjoy tariff-free trade with the country's biggest export market.But all face uncertainty as Britain negotiates a new trading relationship with Brussels.Some fear disaster if the talks break down.British carmakers could face a l0%tanff to export to the EU market.Dairies might have to pay tariffs of more than 30%.These extra costs could make exporting uneconomic.The Cambridge paper looks at the exporting decisions of British firms,across 8,000 types of product,in response to the tariffs that Britain would face in the event of reaching no trade deal with the EU.Where necessary,they adjust their calculations to take account of exchange-rate fluctvations.Since the referendum many companies appear to have reduced their exports to the EU.The research suggests that the bigger the potential tariff facing a product,the more nervous:firms are about exporting it.Why risk producing for a market that could soon become unwelcoming?Overall,the number of companies that began exporting new products to the EU in 2016 would have been 5%higher if there had been a Remain vote,the paper finds.It is hard to know what those firms that decided against producing for the EU did instead.The research finds little evidence,however,that they have lived up to the hopes of Brexiteers and boosted their exports to fast-growing non-EU markets.Some may have tried to sell more within Britain.Businesses may have only temporarily scaled down their production of exports for the EU.Normal service could resume ifBritain negotiates a good trade deal.But some damage is already done.The paper's results imply that in 2016 Britain lost some~lbn（$1.3bn）of exports to the EU because of the mere threat of higher tariffs.The long-term impact will be greater.Some of the firms dissuaded from exporting would have turned into big beasts.The referendum was only halfway through 2016,and the paper does not analyse data after that year.Meanwhile,Brexit uncertainty continues to rise.
We may learn from the paper that______

A.it focuses on Britain's exporting decisions
B.the higher the tariffs,the less exporters
C.Remain vote may promote export to EU
D.hopes ofBrexiteers are quickly fading

微循环中与体温调节有关的关键组成部分是

A.后微动脉
B.通血毛细血管
C.动-静脉吻合支
D.真毛细血管