题目内容
（请给出正确答案）
Why there are fewer plants, trees and flowers in Holland now？
A．Because there has been a lot of pollution there.
B．Because there was a shortage of water.
C．Because many plants, trees and flowers have been destroyed.
D．Because Holland does not need so many plants, trees and flowers.
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更多“Why there are fewer plants, tr…”相关的问题
A. it's full
B. Good question
C. I bet that was fun
D. Good idea
E. I used to
F. fewer cars
G. Look
H. Hey
A: Why is there never a bus when you want one？
B: (56) . There aren't enough buses on this route.
A: Sometimes I feel like writing a letter to the paper.
B: (57) . You should say that we need more subway lines, too.
A. Yeah. There should be more public transportation in general.
B: And (58) ! There's too much traffic.
A: (59) , is that our bus coming？
B: Yes, it is. But look, (60)
A: Oh, no! Let's go and get a cup of coffee. We can talk about this letter I'm going to write.
According to this law, changes in the prices of goods cause change in supply and demand. An increase in the price of the goods causes an increase in supply-then number of goods the producers make. Producers will make more goods when they can get higher prices for the goods. The producer makes more shoes as the price of shoes goes up. At the same time, an increase in the price of the goods causes a decrease in demand—the number of goods the consumers buy. This is because people buy less when the price is high. People buy fewer shoes as the price of shoes goes up. Conversely, a decrease in the price causes an increase in demand (people buy more shoes) and a decrease in supply (producers make fewer shoes).
Business firms look at both supply and demand when they make decisions about price and production. They look for the equilibrium point where supply equals demand. At this point, the number of shoes produced is 3000 and the price of the shoes is $30. $30 is the equilibrium price: at this price the consumers will buy all of the 3000 shoes which the producers make. If the producers increase the price of the shoes, or if they produce more than 3000 shoes, the consumers will not buy all of the shoes. The producers will have a surplus(过剩)—more supply than demand—so they must decrease the price in order to sell all of the shoes. On the other hand, if they make fewer than 3000 shoes, there will be a shoes shortage —more demand than supply—and the price will go up.
According to the Law of Supply and Demand, the equilibrium price is the best price for the good. The consumers and the producers will agree on this price because it is the only price that helps them both equally.
Why does an increase in price cause an increase in supply？ ______
A．Consumers buy more goods when prices are high.
B．Producers make more goods when prices are high.
C．Producers want to sell all of their goods.
D．Consumers will not buy all of the goods.
Radiocarbon Dating
Nowadays scientists can answer many questions about the past through a technique called radiocarbon(放射性碳), or carbon-14, dating. One key to understanding how and why something happened is to discover when it happened.
Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons(质子) and six neutrons(中子) in its nucleus. Carbon-14, or C-14, is a radioactive, unstable form. of carbon that has two extra neutrons(原子核). It returns to a more stable form. of carbon through a process called decay(衰减). This process involves the loss of the extra neutrons and energy from the nucleus.
In Libby's radiocarbon dating technique, the weak radioactive emissions(放射) from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C-14 atoms in the sample being dated.
Carbon-14 is produced in the Earth's atmosphere when nitrogen(氮)-14, or N-14, interacts with cosmic rays(宇宙射线). Scientists believe since the Earth was formed, the amount of nitrogen in the atmosphere has remained constant. Consequently, C-14 formation is thought to occur at a constant rate. Now ratio of C-14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years.
All life on Earth is made of organic molecules(分子) that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues(组织). Once an organism(有机体) dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon atoms goes down. In terms of radiocarbon dating, the fewer C-14 atoms in a sample, the older that sample is.
Nowadays many scientists depend on radiocarbon for dating age-old objects.
A．Right
B．Wrong
C．Not mentioned
Samuel Preston, a sociologist at the University of Pennsylvania, studied how the American family is changing. He reported that by the time the average American couple reaches about 40 years of age, their parents are usually still alive. The statistics show the change in lifestyles and responsibilities of aging (老龄化) Americans. The average middle-aged couple can look forward to caring for elderly parents sometime after their own children have grown up. Moreover, because people today live longer after an illness than people did years ago, family members must provide long-term care. These facts also mean that after caregivers provide for their elderly parents, who will eventually die, they will be old and may require care too. When they do, their spouses (配偶) will probably take care of them because they have had fewer children than their parents did.
Because Americans are living longer than ever, more social workers have begun to study ways of caregiving to improve the care of the elderly. They have found that all caregivers share a common characteristic; They believe that they are the best people for the job. The social workers have also discovered three basic reasons why the caregivers take on the responsibility of caring for an elderly, dependent relative. Many caregivers believe they had an obligation (职责) to help their relatives. Some think that helping others makes them feel more useful. Others hope that by helping someone now, they will deserve care when they become old and dependent.
Samuel Preston's study shows that______.
A．lifestyles and responsibilities of the elderly are not changing
B．most American couples over 40 have no living parents
C．middle-aged Americans have to take care of their children and parents at the same time
D．elderly people may need care for a long time because they live longer after an illness
A.less;less
B.fewer;little
C.less;fewer
D.fewer;fewer
A．less, less
B．fewer, fewer
C．less, fewer
D．fewer, less
A.ollows/obeys;less
B.ollows/obeys;fewer
C.will follow/obey;fewer
A.less
B.fewer
C.many
D.little
