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If you live in a region where winter weather is a regular risk, you are likely used to pouring salt on your sidewalks. But how does it work? And how much salt do humans pour onto our planet’s surface? The second question is easier to answer: a lot.

Salt doesn’t directly melt ice, nor does it make snow simply disappear. Instead it makes water less likely to freeze in a phenomenon called freezing point depression. In the case of simple rock salt, which is a rawer, less pure version of table salt, each molecule (分子) splits into smaller elements. Normally, when water freezes into ice, its molecules line up to form a stable, orderly structure. Salt interrupts the process, however, and temperatures must drop lower to overcome that interruption and for freezing to occur.

But if salt needs to interact with liquid water, how does it do anything when temperatures are stubbornly below freezing, and water should already be in the form of ice? That’s where cars help clear their own way by creating friction and, in turn, heat. The friction allows for the ice that has already frozen to melt a little bit, making it unlikely to freeze.

Beyond rock salt’s ability to clear icy streets, it can also be destructive. Chloride ions (氯离子) can cause wear and tear on vehicles and facilities. Increasing chloride densities in North American lakes could begin to upset local ecology and degrade sources of drinking water.

Many local governments are looking for alternatives to rock salt. Other salts such as magnesium chloride and calcium chloride work in the same way as rock salt, and they’re perhaps even more efficient. Some experiments are testing other ice-preventing solutions, including those that contain sugars instead of or in addition to salts. Another approach relies more heavily on sand, which can mechanically make roads safer. All of this experimentation is aimed at ensuring people can travel in any weather condition — a Herculean task when winter brings its worst.

【小题1】What’s the purpose of the first sentence in Paragraph 2?
A.To introduce the topic.B.To give some evidence.
C.To define the phenomenon.D.To reveal the misconception.
【小题2】How does salt work to disturb the process of freezing?
A.By lowering the temperature.B.By melting and splitting itself.
C.By lining up to form a solid structure.D.By stopping the formation of the structure.
【小题3】What does the underlined word “densities” in Paragraph 4 mean?
A.Concentrations.B.Weights.C.Qualities.D.Salts.
【小题4】What’s the last paragraph mainly talking about?
A.Other salts won’t disturb local ecology.
B.Efforts are being made to guarantee safe travels.
C.Many alternatives are available to solve the problem.
D.Bitter winter make it impossible to secure road safety.
2024·全国·二模
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Why people collect art

Many people throughout history have gone to great lengths to collect art. But what attracts these collectors?

One popular explanation for collecting is that they can have financial(财务的) gain. Some resell works, earning enormous profit.【小题1】 Some “collectors" even buy art as a form of money laundering, since it is far easier to move art than cash between countries without examination.

【小题2】 For them, art is important for other reasons. The best way to understand the underlying drive of art collecting is as a way to create and strengthen social bonds, and as a way for collectors to communicate within these new networks.

Collectors are not only interested in creating social links; they are also motivated by the messages they can send once these social networks are created. We all know art is a powerful way for the artist to express thoughts and feelings.【小题3】 Displaying art can send a message about who the collector really is — at least who he or she sees himself or herself as.

【小题4】 Through the collections, collectors convey messages not just about themselves, but about the world as a whole. For example, the kid with the shoebox of bird feathers might show others his or her collection not just to make friends, but also to convince them of the importance of protecting endangered species.

People collect art for various reasons.【小题5】

A.They gain a lot from artworks from different aspects.
B.But most collectors think little of profit.
C.Artworks preserve the qualities of their makers.
D.No doubt art collection is a hard addiction to overcome.
E.Some get large tax reductions for donating art to museums.
F.It also serves as an effective way for collectors to express themselves.
G.Other art collectors see their collections as having broader power.
Directions: Complete the following passage by using the sentences given below. Each sentence can be used only once. Note that there are two more sentences than you need.

The North Star

Among the pile of stars in the universe, there are a couple that are of great importance to people on Earth. The sun, of course, is one of them. The other is known as Polaris, the North Star. 【小题1】. Therefore, it is a great compass(指南针).When people in the northern part of Earth look toward Polaris, they can be certain that they are facing north. The permanence of Polaris in the north sky has helped countless people find their destinations.

Before the invention of modern navigation tools, sailors relied on Polaris. From the top of their ships, sailors would look for Polaris to figure out their place at sea. They figured out the angle between the star and the horizon to determine their latitude(纬度). As long as the equations were not wrong, the results were very reliable. Polaris also let sailors determine North, South, East, and West. 【小题2】

To those who sail at night, changeable storms and dark clouds were more than annoying things.【小题3】.It’s possible for a captain to make an accidental wrong turn. The ship could become stranded at sea, and the frustrated captain would have no way to get the ship back on the right course. The sailor’s fears wouldn’t be relieved until the clouds cleared and Polaris came back into view. Even today, sailors sometimes choose to steer by using Polaris on clear nights.

【小题4】. The Big Dipper, a constellation that is well known in astrology, appears to revolve around Polaris. The handle of the Big Dipper always points to the North Star. When people get lost, it’s comforting to know that their problems can be relieved by looking at the sky.

A.It’s not difficult to tell the Polaris apart from the pile of other stars in the universe.
B.People who are lost can be relieved by gazing up at Polaris.
C.By knowing directions and their location, sailors could easily steer their ships.
D.They could destroy entire journeys by blocking the view of Polaris.
E.It’s certain that the Polaris is part of a constellation(星座), which is not far from it.
F.It is special because it is the only star that always appears to be in the same place in the sky.

The Smart Treat Chocolate lovers know that eating chocolate makes them happy. Now it turns out that eating chocolate may also make them smarter. Dr. Bryan Raudenbush recently conducted a study to see how eating chocolate affects people’s brains. The U.S. researchers knew that chocolate contained several stimulants. But he wasn’t sure how those stimulants actually affected chocolate eaters. To find out, Raudenbush had a group of volunteers eat 85 grams of milk chocolate. He asked another group to eat no chocolate at all. After 15 minutes, he tested their memory and their ability to solve problems. The group that ate milk chocolate had higher scores. They were able to remember more words and pictures than the group that did not eat chocolate. Raudenbush concluded that the stimulants in chocolate increased mental alertness. Of course, eating chocolate doesn’t guarantee you’ll pass every test. You’ll still need to study!

【小题1】We can learn from the passage that ________.
A.chocolate can help people pass every test
B.chocolate lovers are smarter than those who don’t love chocolate
C.chocolate can make people happy and cleverer
D.chocolate is loved by all the people
【小题2】Why did Dr. Bryan Raudenbush conduct a study recently?
A.Because chocolate contains several stimulants.
B.Because chocolate made him happy.
C.To make himself smarter by eating chocolate.
D.To find out how people’s brains are affected by eating chocolate.
【小题3】The word stimulants belongs to ________.
A.medicineB.vegetableC.commercialD.identification
【小题4】The author wrote the article mainly to express that ________.
A.chocolate is good for health
B.chocolate tastes better with milk
C.people’s performance can be improved by eating chocolate
D.nothing else can be more tasty and effective than chocolate

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