题目内容
Section A
Directions: In this section, you will hear 8 short conversations and 2 long conversations. At the end of each conversation, one or more questions will be asked about what was said. Both the conversation and the questions will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A, B, C and D, and decide which is the best answer.
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Dark Forces Dominate Universe
The earth, moon, sun and all visible stars in the sky make up less than one percent of the universe. Almost all the rest is dark matter and dark energy, unknown forces that(51)astronomers.
Observations in recent years have changed the basic(52)of how the universe evolved and have indicated how little is known about the major forces and substances that(53)our world.
Astronomers now know that luminous (发光的) matter -- stars, planets and hot gas -- accounts(54)only about 0.4 percent of the universe. Non-luminous components, such as black holes and intergalactic (星系间的) gas,(55)up 3.6 percent. The rest is either dark matter, about 23 percent, or dark energy, about 73 percent.
Dark matter, sometimes(56)"cold dark matter," has been known for some time. Only recently have researchers come to understand the key role it(57)in the formation of stars, planets and even people.
"We(58)our very existence to dark matter," said physicist Paul Steinhardt and a co-author of a review on dark matter which(59)not long ago in the journal Science.
"Dark matter dominated the structure(68)in the early universe," Steinhardt said. "For the first few billion years dark matter contained most of the mass of the universe. You can think of ordinary matter(61)a froth (泡沫) of an ocean of dark matter. The dark matter clumps (结成块) and the ordinary matter falls into it. That(62)to the formation of the stars and galaxies (星系)."
Without dark matter, "there would be virtually no structures in the universe."
The nature of dark matter is(63). It cannot be seen or detected directly. Astronomers know it is there because of its(64)on celestial (天体的) objects that can be seen and measured.
But the most dominating force of all in the universe is called dark energy, a recently(65)power that astronomers say is causing the galaxies in the universe to separate at a faster and faster speed.
Ocean Noise Pollution
Some scientists say that animals in the ocean are increasingly threatened by noise pollution caused by human beings.
The noise that affects sea creatures comes from a number of human activities. It is caused mainly by industrial underwater explosions, ocean drilling, and ship engines. Such noises are added to natural sounds. These sounds include the breaking of ice fields, underwater earthquakes, and sounds made by animals themselves.
Decibels (分贝) measured in water are different from those measured on land. A noise of one hundred-twenty decibels on land causes pain to human ears. in water, a decibel level of one-hundred ninety-five would have the same effect.
Some scientists have proposed setting a noise limit of one-hundred-twenty decibels in oceans. They have observed that noises at that level can frighten and confuse whales (鲸鱼).
A team of American and Canadian scientists discovered that louder noises-can seriously injure some animals; The research team found that powerful underwater explosions were causing Whales in the area to lose their hearing. This seriously affected the whales' ability to exchange information and find their way. Some of the whales even died. The explosions had caused their ears to bleed (出血) and become infected (感染).
Many researchers whose work depends on ocean sounds object to a limit of one-hundred-twenty decibels. They say such a limit is a greater danger than they believed. They want to prevent noises from harming creatures in the ocean.
According to the passage, which of the following is increasingly dangerous to sea creatures？
适用于承受荷载较小、变形不大的设备基础的是()。
《机电设备安装工程施工及验收通用规范》规定，设备安装工程应按设计施工。当施工时发现设计有不合理之处，应及时提出修改意见，并经()批准后，方可按变更后的设计施工。
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