The Peppered Moth, a kind of insect (昆虫), is found in England. It is light brown in color and likes living in trees which are also light brown. It’s difficult for birds to notice and eat it.

But with the development of industry (工业), smoke from factories began to reach the trees where the moth lived. It made the trees blacker. Then something very strange took place: in industrial areas, the Peppered Mouth began to change color. It became darker as well. Though the change took several years.

A scientist called Kettlewell decided to make a careful study of this. He marked some of the light moths and some of the darker ones, and set them free in the woods near Birmingham, an industrial city.

Later, he re-caught as many the marked moths as possible. (The results were given in the chart.)

The research was done in the early 1950s. Soon the UK made new laws to reduce (或少) smoke and factory pollution.

Can you imagine what would happen to the Peppered Moth as the air became cleaner again?

Etymology (语源), the study of words and word roots, may sound like the kind of thing done by boring librarians in small rooms. Yet etymologists actually have an interesting job. They are in many ways just like archaeologists (考古学家) digging up the history of people and events. The special aspect of etymology is that it digs up history, so to speak, through the words and phrases that are left behind.

The English language is a great field to explore history through words. As a language, English has a number of words. In some way, this is because it has its ability to adapt (适应) foreign words so easily. For example, “English” words such as kindergarten (from German), croissant (from French), and cheetah (from Hindi) have become part of the language with little or no change from their original (最初的) sounds and spellings. So English-language etymologists have a large world of words to explore.

Another enjoyable thing about etymology for most word experts is solving word mysteries (谜). No, etymologists do not go around solving murders (谋杀), like the great detective (侦探) Sherlock Holmes. What these word experts solve are mysterious origins of some of our most common words.

One of the biggest questions English language experts have pursued is how English came to have the phrase OK. Though it is one of the most commonly used expressions, its exact beginning is a puzzle even to this day. Even its spelling is not completely consistent(吻合的)—unless you spell it Okay, it is hard even to call it a word.

Etymologists have been able to narrow OK’s origin down to a likely, although not certain, source (来源). It became widely used around the time of Martin Van Buren’s run for president in 1840. His nickname (昵称) was Old Kinderhook. What troubles word experts about this explanation is that the phrase appeared in some newspapers before Van Buren became well known. It is likely that Van Buren could be called its primary source. Etymologists will doubtlessly keep searching for the original source. However, it is clear that OK’s popularity and reputation (名声) have topped those of the American president to whom it has been most clearly connected with.

In our daily life, we often have such an experience: When we want to eat, being busy, we fight with the hunger. But when we’ve been hungry for a long time, we find us no longer hungry. Why does the sense of hunger go away even if we don’t eat?

Why are people hungry? From a scientific point of view, the food we eat is changed into glucose(葡萄糖) for energy, and we feel hungry because we don’t have enough sugar. Our bodies can feel how much glucose there is in the blood. When there is not enough glucose, a person feels hungry. Hunger is not caused by having less food in the stomach, but the changes in glucose levels. So when you’re hungry, you don’t have to have meals.

When we have been hungry for a long time, why aren’t we hungry? In fact, the spare glucose can be stored. When we can’t eat for some reasons, our body will change these stored sugar into energy. When it arrives at a certain stage, our body will give us a message: the glucose is enough. So we don’t feel hungry anymore.

Is it OK not to eat when you’ve been hungry for a long time? No. It is harmful to the human body. When the stored energy is used up, the body breaks down fat(脂肪) to provide itself with energy. During this process, the person will feel dizzy. If worse, the protein(蛋白质) which is very important to the body also starts to break down, and we are in danger. If the worst, we may lose our lives.

For busy people, take some sweets with you on rainy days. If you have been hungry for too long, you mustn’t give up eating! Start with a piece of candy or some soup.

A．

B．

C．

D．