单选题
单选题
Lots of creatures already reproduce without sex. Since the birth of Louise Brown, the first test-tube baby, in 1978, (1) of human beings (2) in laboratory glassware rather than in bed.
If human cloning becomes possible—and since the birth of a sheep called Dolly, (3) doubt that it will be feasible to clone a person by 2025—even the link between sex organs and reproduction (4) . You will then be able to take a cutting from your body and grow a new person, (5) you were a willow tree.
(6) , we have already divorced sex from reproduction. In the 1960s, the contraceptive pill freed women to enjoy sex for its own sake. (7) , greater tolerance of homosexuality signaled society’s acceptance of nonreproductive sex of another sort. These changes are only continuations of a (8) that started perhaps a million years ago.
Human beings (9) the interest in infertile, social sex with a few other species: dolphins, apes and some birds. But (10) sex is too good for human beings to (11) , more and more people will abandon it as a (12) of reproduction.
In the modern world, you can (13) have sex and parenthood without suffering the bit (14) . Some Hollywood actresses (15) the urge for mothering by electing to adopt children (16) spoil their figures (as they see it) by childbearing. For people as beautiful as this, the temptation to (17) a clone (reared in a surrogate womb) could one day be (18) .
However, human cloning and designer babies are probably not (19) . Even assuming that the procedures are judged safe and efficient in farm animals, still a long way off, they will be heavily (20) , if not banned, by many governments for human beings.
A:is broken B:will break C:will be broken D:will have broken
News reports say peace talks between the two countries ______ with no agreement reached.
A:have broken down B:have broken out C:have broken in D:have broken up
Regeneration of Limbs Most people would agree that it would be wonderful if humans could regenerate limbs. Those who have lost their arms or legs would be complete again. The day is still far off when this might happen. But in the last 10 years, doctors have reported regeneration in smaller parts of the body, most often fingers. Regeneration is not a newly-discovered process. For centuries, scientists have seen it work in some kinds of animals. Break off a lizards (蜥蜴的) tail, for example, and it will grow a new tail. Scientists now are looking for a way to turn on this exciting ability in more highly-developed animals, including humans. Their experiments show that nerves, cell chemistry and the natural electric currents in the body all seem to have a part in this process. The body of every animal contains general purpose cells that change into whatever kind of cells the body needs. Animals such as the lizard or salamander (蝾螈) use these cells to regenerate a new tail or leg when the old one is broken off. These cells collect around the wound. They form a mass called a blastema (胚基). The cells of the blastema begin to change. Some become bone cells, some muscle cells, some skin cells. Slowly, a new part re-grows from the body outward. When completed, the new part is just like the old one. More than 200 years ago, Italian scientist Luigi Spallanzani showed that younger animals have a greater ability to regenerate lost parts than older animals. So do animals lower on the ladder of evolutionary development. The major difference seems to be that less-developed animals have more nerves in their tails and legs than humans do in their arms and legs. Another helpful piece of information was discovered in the late 1800s. Scientists found that when a creature is injured, an electrical current flows around the wound. The strength of the current depends on how severe the wound is and on how much nerve tissue is present. In 1945, American scientist Meryl Rose tested another idea about regeneration. He thought a new limb might grow only from an open wound. Doctor Rose cut off the front legs of some frogs, below the knee. He kept the wounds wet with a strong salty liquid. This prevented skin from growing over the wounds. The results were surprising. Frogs do not regenerate new legs naturally. But these frogs began to grow new limbs. About half of each cut-off leg grew back again. New bones and muscles developed. This research has led doctors to new ways of treating cut-off fingers. Doctors have observed, for example, that many children and some adults will re-grow the top of a finger if the wound is left open. Which of the following statements is NOT true?
A:Scientists have lately found that a lizard will grow a new tail if the old one is broken off. B:Regeneration is a process discovered centuries ago. C:How severe a wound is determines the strength of the current flowing around it. D:The lizard, unlike man, is a less-developed animal.
According to the latest report, the talks have collapsed.
A:broken away B:broken down C:broken in D:broken out
According to the latest report, the talks have {{U}}collapsed{{/U}}.
A:broken away B:broken down C:broken in D:broken out
Regeneration of Limbs Most people would agree that it would be wonderful if humans could regenerate limbs. Those who have lost their arms or legs would be complete again. The day is still far off when this might happen. But in the last 10 years, doctors have reported regeneration in smaller parts of the body, most often fingers. Regeneration is not a newly-discovered process. For centuries, scientists have seen it work in some kinds of animals. Break off a lizards (蜥蜴的) tail, for example, and it will grow a new tail. Scientists now are looking for a way to turn on this exciting ability in more highly-developed animals, including humans. Their experiments show that nerves, cell chemistry and the natural electric currents in the body all seem to have a part in this process. The body of every animal contains general purpose cells that change into whatever kind of cells the body needs. Animals such as the lizard or salamander (蝾螈) use these cells to regenerate a new tail or leg when the old one is broken off. These cells collect around the wound. They form a mass called a blastema (胚基). The cells of the blastema begin to change. Some become bone cells, some muscle cells, some skin cells. Slowly, a new part re-grows from the body outward. When completed, the new part is just like the old one. More than 200 years ago, Italian scientist Luigi Spallanzani showed that younger animals have a greater ability to regenerate lost parts than older animals. So do animals lower on the ladder of evolutionary development. The major difference seems to be that less-developed animals have more nerves in their tails and legs than humans do in their arms and legs. Another helpful piece of information was discovered in the late 1800s. Scientists found that when a creature is injured, an electrical current flows around the wound. The strength of the current depends on how severe the wound is and on how much nerve tissue is present. In 1945, American scientist Meryl Rose tested another idea about regeneration. He thought a new limb might grow only from an open wound. Doctor Rose cut off the front legs of some frogs, below the knee. He kept the wounds wet with a strong salty liquid. This prevented skin from growing over the wounds. The results were surprising. Frogs do not regenerate new legs naturally. But these frogs began to grow new limbs. About half of each cut-off leg grew back again. New bones and muscles developed. This research has led doctors to new ways of treating cut-off fingers. Doctors have observed, for example, that many children and some adults will re-grow the top of a finger if the wound is left open. Which of the following statements is NOT true?
A:Scientists have lately found that a lizard will grow a new tail if the old one is broken off. B:Regeneration is a process discovered centuries ago. C:How severe a wound is determines the strength of the current flowing around it. D:The lizard, unlike man, is a less-developed animal.
A:eight broken B:broken eight C:eight new D:new eight
