单选题 太空垃圾(space trash)是指那些绕着地球飞行的无用处的人造物体。这些物体在太空中不断碰撞，产生更多的太空垃圾，不仅给航天事业带来了巨大隐患，而且还污染了宇宙空间，给人类带来灾难。目前移除太空垃圾的方法主要有自然移除和人为移除，但效果都不理想。最好的方法就是从源头杜绝卫星成为太空垃圾的可能性，只有这样才能保证人类航天事业的可持续发展。

单选题She was so ______ in her job that she didn't hear anybody knocking at the door. A. attracted B. absorbed C. drawn D. concentrated

单选题It was sunrise on an August morning when the captain and his crew cast their nets some 50 miles south of Louisiana in the Gulf of Mexico. As the net was pulled over, the contents were poured out follo

单选题Even plants can run a fever, especially when they're under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away --straight up. A decade ago, adapting the infrared scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide (杀虫剂) spraying rather than rain poison on a whole field, which invariably includes plants that don't have pest (害虫) problems. Even better, Paley's Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were transformed into a color-coded map showing where plants were running "fevers". Farmers could then spot-spray, using 40 to 70 percent less pesticide than they otherwise would. The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States." says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago.

单选题She was so______in her job that she didn" t hear anybody knocking at the door.

单选题When the air in a certain space is squeezed to occupy a smaller space, the air is said to be______.

单选题Woman: So, how are you getting along with Jane's cat? Man: Well, she never comes when I call her, she spills her food, and she sheds all over the place. I can't wait till Jane gets back. Question: What does the man imply?

单选题The biggest safety threat facing airlines today may not be a terrorist with a gun, but the man with the portable computer in business class. In the last 15 years, pilots have reported that well over 100 incidents could have been caused by electromagnetic interference. The source of this interference remains unconfirmed, but increasingly, experts are pointing the blame at portable electronic device such as portable computers, radio and cassette players and mobile telephones. RTCA, an organization which advises the aviation (航空) industry, has recommended that all airlines ban (禁止) such devices from being used during "critical" stages of flight, particularly take-off and landing. Some experts have gone further, calling for a total ban during all flights. Currently, rules on using these devices are left up to individual airlines. And although some airlines prohibit passengers from using such equipment during take-off and landing, most are reluctant to enforce a total ban, given that many passengers want to work during flights. The difficulty is predicting how electromagnetic fields might affect an aircraft"s computers. Experts know that portable device emit radiation which affects those wavelengths which aircraft use for navigation and communicatioa But, because they have not been able to reproduce these effects in a laboratory, they have no way of knowing whether the interference might be dangerous or not. The fact that aircraft may be vulnerable (易受损的) to interference raises the risk that terrorists may use radio systems in order to damage navigation equipment. As worrying, though, is the passenger who can"t hear the instructions to turn off his radio because the music"s too loud. (275 words)

单选题What do the words "remain stationary" mean in sentence 1, paragraph 4 of the passage?

单选题Families in frontier settlements used to entertain strangers ______.

单选题One weakness of this study may be ______.

单选题How do flying foxes care for the young ones? ( )

单选题It is (necessary) that the (customs) (of all) nations (must be respected).A. necessaryB. customsC. of allD. must be respected

单选题This research has attracted wide ______ coverage and has featured on BBC television' s Tomorrow' s World. A. message B. information C. media D. data

单选题In mountainous regions, much of the snow that falls is Ucompacted/U into ice.

单选题I'd rather you ______ make any comment on the issue for the time being. A. don't B. wouldn't C. didn't D. shouldn't

单选题 A bull grazes on dry wheat husks in Logan, Kansas, one of the regions hit by the record drought that has affected more than half of the U.S. and is expected to drive up food prices. Leading water scientists have issued one of the sternest warnings yet about global food supplies, saying that the world's population may have to switch almost completely to a vegetarian diet over the next 40 years to avoid catastrophic shortages. Adopting a vegetarian diet is one option to increase the amount of water available to grow more food in an increasingly climate-unstable world, the scientists said. Animal protein-rich food consumes 5 to 10 times more water than a vegetarian diet. One third of the world's arable (适于耕种的) land is used to grow crops to feed animals. Other options to feed people include eliminating waste and increasing trade between countries in food surplus and those in deficit. '900 million people already go hungry and 2 billion people are malnourished in spite of the fact that per capita food production continues to increase, ' they said. 'With 70% of all available water being in agriculture, growing more food to feed an additional 2 billion people by 2050 will place greater pressure on available water and land.' The report is being released at the start of the annual world water conference in Stockholm, Sweden, where 2, 500 politicians, UN bodies, nongovernmental groups and researchers from 120 countries meet to address global water supply problems. Competition for water between food production and other uses will intensify pressure on essential resources, the scientists said, 'The UN predicts that we must increase food production by 70% by mid 21th century. This will place additional pressure on our 'already stressed water resources', at a time when we also need to allocate more water to satisfy global energy demand—which is expected to rise 60% over the coming 30 years—and to generate electricity for the 1.3 billion people currently without it, ' said the report. Overeating, undernourishment and waste are all on the rise and increased food production may face future constraints from water scarcity. 'We will need a new recipe to feed the world in the future, ' said the report's editor, Anders Jagerskog. A separate report from the International Water Management Institute (IWMI) said the best way for countries to protect millions of farmers from food insecurity in sub-Saharan Africa and south Asia was to help them invest in small pumps and simple technology, rather than to develop expensive, large-scale irrigation projects. 'Farmem across the developing world are increasingly relying on and benefiting from small-scale, locally-relevant water solutions. These techniques could increase yields up to 300% and add tens of billions of U. S. dollars to household revenues across sub-Saharan Africa and south Asia.' said Dr. Colin Chartres, the director general.