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Frogs are important in the ecosystem because they control pests.A．YB．NC．NG
Frogs are important in the ecosystem because they control pests.
A．Y
B．N
C．NG
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题目内容
（请给出正确答案）
Frogs are important in the ecosystem because they control pests.
A．Y
B．N
C．NG
答案
更多“Frogs are important in the ecosystem because they control pests.A．YB．NC．NG”相关的问题
第1题
Frogs and toads are usually poisonous.
A．Y
B．N
C．NG
第2题
Biologists are unable to explain why frogs are dying.
A．Y
B．N
C．NG
第3题
The frogs' natural habitat is becoming more and more developed.
A．Y
B．N
C．NG
第4题
A．the clouds over the forest of neighboring Nicaragua
B．computer simulations of day
C．the gradual shifting of bird living upslope
D．a recent population decrease of frogs and toads
第5题
One of the【C1】______ beautiful sights in the bird world is the male peafowl, or peacock, strutting (炫耀) proudly【C2】______ with its magnificent【C3】______ raised and its richly【C4】______ tail feathers【C5】______ in the sunlight. The peacock's many colored "tail" is not really a tail at【C6】______. It is a fan【C7】______ of stiff, beautiful feathers. This fan is【C8】______ by the peacock's true tail. In【C9】______ to the glorious plumage, a peacock has a crest of upright feathers on its head.【C10】______, the peahen, or female peafowl, is usually colored a dull brown and has neither【C11】______ nor crest.
The peafowl is a member of the pheasant【C12】______. It may be found【C13】______ wild in the jungles of Asia and of the East Indies. Tame peafowl may be seen in nearly all other parts of the world,【C14】______, although their flesh and their eggs are【C15】______ good for【C16】______ use, they are generally kept【C17】______ ornaments or curiosities in parks and in zoos. Peafowl in a wild state feed【C18】______ grass, grain, frogs, insects and snails. In【C19】______, however, they thrive on grains commonly【C20】______ to poultry.
【C1】
A．many
B．more
C．most
D．much
第6题
ACID RAIN: What's the Solution？
One of the wildest regions in the U.S., far from civilization, is the Adirondack area of northern New York State. For years this isolated spot has had the reputation of being one of best fishing spots in the U.S.
As a boy 30 years ago, Bill Marleau first through the Adirondack wilderness near his small cabin on Woods Lake. Thousands of sportsmen have stayed at his father's lodge nearby.
But now Bill's 134 hectares (335 acres) of lakefront land have only scenic value. Gone are those huge trout that used to swim in the turbulent, nutrientrich water a short distance from his doorstep. Gone from the cool nights are the sounds of thousands of frogs and toads.
And gone are the birds that once fed on those water creatures.
Occasionally Bill sees a lone fisherman fruitlessly cast his bait into the empty waters of old lake. "I just don't have the heart to tell," he said. "This old lake's dead. It was killed years ago by acid rain." What is acid rain？
Acid rain is a popular term for precipitation in the form. of rain, sleet, snow or hail that is more acidic than normal. Acid rain is produced when atmospheric moisture combines with pollutants from power plants, factories and automobiles.
When fossil fuels such as coal and oil are burned, sulfur dioxide and nitrogen dioxide are produced. These two gases react with the water and oxygen in the atmosphere to form. droplets of weak sulfur and nitric acid.
Carried by prevailing winds and weather conditions, clouds containing these droplets travel hundreds, sometimes thousands, of kilometers from the source of the pollutants. Recently scientists found that acid rain now affects huge areas of the North Hemisphere.
Power plants and factories in the heavily industrialized regions of Ohio and Indiana are believed to be the source of the acid rain that killed Woods Lake along with hundreds of others in New York State and eastern Canada. Acid haze over Alaska is believed to come all the way from Japan. And precipitation as acid as vinegar that falls on Scotland and Scandinavia probably originates in England.
How Acidity Is Measured
Scientists measure the acidity of rain in pH units. A pH scale from 0 to 14 is used. Depending upon its chemical composition, a solution is either acidic, alkaline (basic), or neutral. Distilled water, which has a pH of 7, is neutral. Substance with pH values less than 7 are acidic, while those over 7 are alkaline.
Normal rain water with a pH of 5.6 is slightly acidic. But after reacting with industrial pollutants, particularly sulfur dioxide, the pH of rain quickly drops.
When acid rain falls to Earth, much of it ends up in lakes and ponds. In addition to failing directly into a lake, acid rains runs off land into streams and rivers that eventually flow into lakes and ponds. Once acid rain gets into them, its effects can be deadly.
Studies started in 1975 in the Adirondacks indicate that salamanders and frogs are the first to die when the pH is lowered. Normally the pH of a lake is 8,0 slightly alkaline. When the pH drops to 7, the eggs of salamanders and frogs fail to hatch. At pH 6.6 snails begin to die.
Bacteria that decompose leaf matter die too, and the leaf matter collects on the lake bottom. As the acidity continues to drop, ail the major food chains in the lake become affected. In time all the fish die.
Eventually primitive, oxygenconsuming plants nearly choke out all other aquatic greenery. Algae and fungal growth that thrive in an acidic environment move in and cover the entire bottom of the now destroyed lake.
Looking like blue vinegar, the lake is now an entirely changed ecosystem. It contains no life expect the fungal and algal growth and a few surfacedwelling water bugs.
&n
A．Y
B．N
C．NG
第7题
听力原文： Rats are the enemy of human beings. They eat or spoil crops of grain and rice before they can be harvested, or while they are in storage. In India, where millions of people go hungry, there are ten times as many rats as people. Rats devour half of the available food. Rats will also attack birds and animals, from frogs and chicks to geese and young calves. They have even destroyed dams and buildings by making holes through or under them, and have started fires by chewing on electrical wiring.
The most terrible destruction caused by rats, however, has come from the diseases they carry. In the fourteenth century, rats caused the death of one-third of the world's population by transmitting the dreadful Black Plague that mined Europe.
Ironically, it is in fighting diseases that rats have been most useful to humanity. Thousands of specially bred rats are used in research laboratories every year to test medicines which can possibly be used to prolong and improve human life. Some laboratory rats are even used to test new methods of eliminating their cousins, the wild rats.
(23)
A．The Black Plague.
B．Enemy of Humanity.
C．Common Animal pests.
D．Causes of World Hunger.
第8题
听力原文： I want to talk today about some studies. They seem to indicate that there is a startling world-wide decline in the number of amphibians, such as frogs, toads and salamanders. There's little doubt that one reason why the number of amphibians is declining is their habitats have been destroyed when the developers fill in ponds and marshes to build houses. Amphibians can't just move somewhere. They need water to lay their eggs in. Another problem is the growing fish industry. Another range of popular pool fish such as carp have been introduced to many lakes and ponds all over the world. Raising and selling these fish can be profitable, but the fish eat the eggs and offspring of amphibians that were already living in the lakes and ponds. Other factors could be contributing to the decline include acid rain and the spread of pesticide residues. Many pesticides that farmers added to their crops are eventually washed away by the rain and end up in ponds and other bodies of water where amphibians live. Amphibians are especially vulnerable to pesticides dissolved in the water because of their moist skins. Water can pass through amphibians allowing toxins dissolved in the water to enter the amphibians' body.
What does the speaker mainly discuss？
A．The distribution of different species of amphibians.
B．Possible reasons for reduction in the number of amphibians.
C．The effects of environmental change on the fish industry.
D．Guidelines for the responsible use of pesticides.
第9题
听力原文： Yokoi Shoichi, a Japanese soldier during World War Ⅱ, never surrendered, For twenty-seven years, he hid deep in the jungles of Guam, a Pacific island battle site during the war. Shoichi stayed there, away from friends and foes alike, because he felt " shame and dishonor" after the war.
Shoichi knew that Japan had lost the war, but the humiliation of defeat kept him from surrendering. So he stayed in the jungle, living on what he could search out. He ate mostly insects, snails, frogs and rats.
In 1972, U.S. authorities finally convinced Shoichi to "surrender". He was sent back to his homeland. Shoichi's returning home attracted a lot of attention. When a department store in Tokyo exhibited his jungle clothes and tools, more than 350 000 curious people came to view them. After spending some time back in civilization, Shoiehi met a forty-five years old widow. The old soldier and the widow fell in love and married. After their wedding, the couple took a honeymoon trip to the island of Guam.
(26)
A．The island of Guam:
B．Yokoi Shoichi's marriage.
C．The battles on Guam during World War Ⅱ
D．A Japanese soldier who hid on Guam.
