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① . The beginnings of life provide scientists with some of the most difficult questions of modern science. Our knowledge of the development of cells, from which all forms of life are made, is not complete because we do not understand very well the conditions on our planet four billion years ago. Why and how did cells first appear? Was this very probable to happen under the conditions then? Might this happen in other places in the universe(宇宙)?     

② . A group of scientists at University College London are trying to answer these questions. They started by studying the ways in which the first cells on the Earth might have been formed. Next they will use a powerful new telescope(望远镜) to look at places far away in the universe. The scientists hope that the results will improve our understanding of the development of life on the Earth and help us to find similar conditions for life development on other planets.

③ . Dr Nick Lane, who is in charge of(负责) the University College London team, has suggested that 4 billion years ago warm water springs(泉) on the floor of the Earth’s ocean might have helped to create life. Each spring consists of tiny connected holes that water passes through. The team has created models of these springs with these holes in their lab. They have found that they encourage chemical reactions(反应) between hydrogen(氢) in the liquids(液体) that come out of them and the carbon dioxide(二氧化碳) in the sea water.

④ . These building blocks are not living themselves, but when there are enough of them joined together in the right way, they can make living things. Water in the system of springs moves the building blocks around until there are a lot of them in a small area. Things that look very much like real living cells can be made in this way.

1．About ________ years ago, different forms of life first appeared on the Earth according to the passage.

A．forty million

B．four billion

C．five million

D．ten billion

2．The scientists search for ________ at places far away in the universe.

A．the same cells found on the Earth	B．suitable places for human to live
C．new forms of life unknown on the Earth	D．similar conditions for life development

3．What does the underlined phrase “consists of” mean in English?

A．is made up of

B．is proud of

C．is satisfied with

D．is famous for

4．It is better to put “These chemical reactions can create the ‘building blocks’ of life.” in ________.

A．①

B．②

C．③

D．④

5．Which of the following is not true according to the last two paragraphs?

A．Enough building blocks joined together in the right way make living things.

B．Water in the system of springs moves the building blocks around till they are in a small area.

C．The building blocks are living themselves and the scientists change them into living cells.

D．Chemical reactions take place between hydrogen and carbon dioxide.