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The primary topic of the passage is which of the following？A．The origin of bioluminescence

The primary topic of the passage is which of the following？

A．The origin of bioluminescence in plankton, predators

B．The disadvantages of bioluminescence in microorganisms

C．The varieties of marine bioluminescent life forms

D．Symbiotic relationships between predators and their prey

E．Hypotheses on the causes of bioluminescence in plankton

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更多“The primary topic of the passa…”相关的问题

第1题

Some people think that young children benefit from going to nursery school before starting

primary school. Others think it is better for them to stay all day with their families. What’s your opinion？ Write a composition of about 200 words on the topic: Is It Better for Children to Go to Nursery School？ You are to write in three parts. In the first part, state specifically what your opinion is. In the second part, support your opinion with appropriate details. In the last part, bring what you have written to a natural conclusion or a summary.

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第2题

听力原文：Prices continued to tumble across the board on local commodities today. The fall

in values has prompted a lot of anxiety in the farming community. The President of the Association of Cattle Farmers has warned that many farmers will face financial ruin if the prices do not recover. After three years of drought, farmers are at a breaking point. Farmers blame the fall in the value of their products on the government relaxing rules on primary commodity imports from developing countries, and a downturn in the economy as a whole. Farmers have warned that if this trend continues, the country will suffer in the long run.

What is the topic of this story？

A．A rally on the stock market

B．Farmers are doing well.

C．Commodities markets are down.

D．It is a good time to buy beef.

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第3题

Most students think of the library only【C1】______a place where books are stored, but a lib

Most students think of the library only【C1】______ a place where books are stored, but a library also【C2】______ many valuable services. The library may loan records and /or films,【C3】______ often houses coin operated photocopying machines; it【C4】______ provide listening rooms, typing【C5】______, and study rooms, Many libraries offer an interlibrary loan system whereby they can borrow books【C6】______ other libraries for your【C7】______.

The people【C8】______ work in a library are perhaps【C9】______ important than any particular thing【C10】______ is kept there. While you may think【C11】______ librarians as people who check【C12】______ and shelve books, you will【C13】______ that college librarians are valuable to talk【C14】______. They can help you locate information, suggest a focus and direction for approaching a topic, and help you organize【C15】______ research. Even though librarians always look【C16】______, do not hesitate to ask them questions. There is always at least【C17】______ librarian, usually located in the reference area,【C18】______ primary responsibility is to【C19】______ students.

Visit the library, look【C20】______, and be ready to use it effectively when you get your first class assignment this semester.

【C1】

A．for

B．as

C．about

D．like

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第4题

Over the past 600 years, English has grown from a language of few speakers to become the d

ominant language of international communication. English as we know it today emerged around 1350, after having incorporated many elements of French that were introduced following the Norman invasion of 1066. Until the 1600s, English was, for the most part, spoken only in England and had not extended even as far as Wales, Scotland, or Ireland. However, during the course of the next two centuries, English began to spread around the globe as a result of exploration, trade (including slave trade), colonization and missionary work. Thus, small enclaves (聚居地) of English speakers became established and grew in various parts of the world. As these communities proliferated, English gradually became the primary language of international business, banking, and diplomacy.

Then came the 20th century and its burst of technology. Suddenly people were talking across oceans, flying across continents, hearing broadcasts that reverberated around the planet. Language spread faster than ever. The world wars carried American and British soldiers around the world, pollinating English as they went. When World War Ⅱ ended, the English language was barreling (高速行驶) forward on the shoulders of American capitalism — McDonald's and Coca-Cola, Rambo and MTV, munitions (军火) and computer technology.

Currently, about 80 percent of the information stored on computer systems worldwide is in English. Two-thirds of the world's science writing is in English, and English is the main language of technology, advertising, media, international airports, and air traffic controllers. Today there are more than 700 million English users in the world, and over half of these are non-native speakers, constituting the largest number of non-native users than any other language in the world.

What is the main topic of this passage？

A．The expansion of English as an international language.

B．The number of non-native users of English.

C．The French influence on the English language.

D．The use of English for science and technology.

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第5题

阅读材料，回答题。Alpha ParticleFrom decaying radon （氡） atoms can destroy the living cells

阅读材料，回答题。

Alpha Particle

From decaying radon （氡） atoms can destroy the living cells they strike and increase the likelihood that those cells will later become cancerous.Researchers have now directly demonstrated that neighboring cells not suffering direct hits can be harmed， too. They"ve also taken a step toward showing how this type of radiation，called alpha particles， indirectly hurts those bystanders.

Radon derives from the decay of uranium （铀） and seeps naturally into the air from the ground.lt"s the primary environmental source of alpha particles， which contribute to cancer risk by causing aberrations （失常）in DNA.Alpha particles from inhaled radon are second only to smoking as a cause of lung cancer.

Because a person"s exposure to alpha particles typically is low， researchers have had to estimate public health threats from radon by guess from the effects of higher doses of alpha radiation.Such data comes primarily from studies of survivors of the atomic bombs that destroyed Hiroshima and Nagasaki in Japan. The customary extrapolation （推测） assumes that cancer risk is proportional to the dose of radiation even at low doses.

Radiation"s effects in cell structure don"t necessarily reflect what happens in "a whole organism， with its full range of defense repair mechanisms， " says Duport.Processes such as DNA repair and cell death triggered by radiation damage could cancel the effect on by stander cells observed in the lab， he suggests.

Furthermore， while a bystander effect can contribute to cancer， other cell-to-cell interactions in living tissue "may relieve increased risk." says Barry Michael， a radiation biophysicist at the Gray Cancer Institute in Northwood， England.One of these interactions halts cell division and hence cancer. "The jury is still out on whether cell-to-cell effects lead to a greater or lower risk， " Michael says.

The passage‘s main topic is__________. 查看材料

A.The experiment done by researchers

B.Uranium is the key killer of neighboring cells

C.Cell-to-cell interaction can make up for the hurt cells

D.Bystander cells can be indirectly damaged by alpha particles

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第6题

初级演替 primary succession

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第7题

原代细胞培养（primary cell culture)

原代细胞培养(primary cell culture)