How many more decades will have to pass ______ scientists succeed in providing a cure for cancer? when since before until

I need______more volunteers to help move the piano. none any few some

______, the book has many mistakes. Having not been written carefully Not writing carefully Having written not carefully Not having been written carefully

As a result of careless washing, the jacket______to a child’s size. compressed shrank dropped decreased

Although he had looked through all the reference material on the subject, he still found it hard to understand this point and her explanation only______ to his confusion. extended amounted added turned

Everybody looked______ the direction of the explosion. to from in into

Trade unions often ______ with employers for better conditions of pay employment. ask require bargain plead

Although the examination he had passed was unimportant, his success______ him in his later study. persuaded promised urged encouraged

You should______ these tables and buy new ones. throw off throw down throw up throw away

Some discussion has______about who should be put in charge of this project. risen lifted raised arisen

There are some______ flowers on the desk. artificial false unreal untrue

______ their suggestions, we will discuss them fully at the next meeting. In regard for In regard to With regard of Regardless for

I have no objection______ your story again. to hear to hearing to having heard to have heard

Peter, who had been driving all day, suggested______ at the next town. to stop stopping stop having stopped

These books, which you can get at any bookshop, will give you______ you need. ail the information all the informations all of information all of the informations

If only I______the books on the reading list before I attended the lecture. have been reading would have read have read had read

I’d just as soon______ that important letter home with you. that you won’t take please don’t you take you not taking you didn’t take

For many years, scientists couldn’t figure out how atoms and molecules(分子)on the Earth combined to make living things. Plants, fishes, dinosaurs(恐龙), and people are made of atoms and molecules, but they are put together in a more complicated way than the molecules in the primitive ocean. What’s more, living things, that have energy and can reproduce on the Earth four billion years ago were lifeless. After years of study, scientists figured out that living things, including human bodies, are basically made of amino acids and nucleotide(氨基酸与核苷酸)bases. These are molecules with millions of hydrogen(氢), carbon(碳), nitrogen(氮), and oxygen atom. How could such complicated molecules have been formed in the primitive soup? Scientists were stumped(难住). Then, in 1953, two scientists named Harold Urey and Stanley L. Miller did a very simple experiment to find out what had happened on the primitive Earth. They set up some tubes and bottles in a closed loop(线圈), and put in some of the same gases that were present in the atmosphere four billion years ago: water vapor, carbon dioxide(二氧化碳), methane(甲烷), and hydrogen. Then they shot an electric spark through the gases to simulate(模拟)bolts(闪电)of lightning on the ancient Earth, circulated the gases through some water, sent them back for more sparks, and so on. After seven days, the water that the gases had been bubbling(起跑)through had turned brown. Some new chemicals were dissolved in it . When Miller and Urey analyzed the liquid, they found that it contained amino acids—the very kind of molecules found in all living things.

Honeybees cannot live alone. Their body structure and instincts equip them for life in a colony(群居)or community, where they have a complex social organization and the various duties are divided among the individuals according to physical fitness and age. An individual worker bee cannot reproduce itself. While it may continue to live if forcibly isolated from its mates， it fails to care for itself adequately(足够), and soon dies. Most insects have the ability to hibernate(冬眠)in winter, but the honeybee seems to have lost this. Since at low temperatures the bee will die, it must have the ability to make its own environment, so far as temperature is concerned. This makes a colony necessary to the bees in winter, so that they may collectively warm each other. Efficiency, if not necessity, demands that the work of the colony be divided, and such a division of labor tends to increase the need to maintain the colony. The physical structure of the honeybee is further suited for the defense of the entire colony rather than for its own defense. The bee’s barbed(有刺的)sting is used only once and is made more effective by the fact that it is left behind in the victim. With the loss of the sting, however, the bee dies. This kind of defensive weapon is not of service to the individual, but to the community.

如果我是他，我就会尽最大的努力按时完成任务。

这所大学提供了他所期望的一切。