When does music in public places become noise pollution? You may like at least some kind of music. But the problem is that, in lots of places, you're made to hear somebody else's choice in music. Say you've just landed at an airport. At the airport, the "background" music may be played loudly. When you are on the way to your hotel, there may be another kind of music played by the taxi driver. Then you finally reach your hotel. But when you are taking the elevator ,there is elevator music. You go out to dinner and end up in a place where the owner of the restaurant thinks music will help make you eat more and spend more. Then a person playing the violin comes around. This is called the "music wallpaper". It is to make you buy more and eat a lot. Even the government thinks this is "noise pollution," especially when the music is too loud. Noise pollution may be bad for our hearing. It's also bad for some of our daily activities, such as sleeping, conversations and so on. The fact that you can't see, taste or smell it may help explain why it has not received as much attention as other kinds of pollution, such as air pollution or water pollution. The air around us is always filled with sounds, but most of us would not think we are surrounded by noise. This can be bad for our health. So many people like soft and quiet music in their house. Music in public places becomes noise pollution because _ . A) it's played at the airport B) it's played by the taxi driver C) it's played when you are taking the elevator D) you are made to hear someone else's choice in music
D

Many animals go on long and difficult journeys to find food or places for their young to start life. They often travel very far, sometimes even halfway around the world. Some animals make one of these amazing journeys every year, while others make only one amazing journey in their lives. Some animals travel over land, some through water and others in the air. Green turtles spend most of their lives in the sea, but they come to the shore to lay their eggs. Every two or three years, fully-grown female turtles swim a long way to the same beach where they were hatched and lay their eggs there. Some turtles may travel over 1240 miles to reach the same beach. No one knows how these turtles are able to find the same beach again. Monarch butterflies live in North America. At the end of summer, they fly south to Mexico. In spring, they fly back north. During this journey, the adults lay their eggs and then they die. When the young butterflies hatch, they continue the journey north. No one knows how the young butterflies know where to go. The journeys for these animals are usually _ . A) long but easy B) short but difficult C) short and easy D) long and difficult
D

DNA is the whole "map" of the human body. It is something that all humans have, and it tells the body what to do. DNA is the reason that we look like our parents, because we get some of their DNA to make our own. People have been trying to understand the human body for a long time. In 1860, Mr. Mendel discovered why we look the same as other people in our family. It is because of small things called "genes" in our body. In 1953, two scientists, Watson and Crick, found out that genes are really messages. They're written in the DNA with a special language. In 1961, another two scientists found the first "word" that they could understand in that language. It shows how DNA tells the cell to build its parts. So far, scientists have found all the words in the DNA map, but we still don't understand what they all do. By understanding what just one "word" means, we can help to save people from several illnesses. So the more we understand, the more doctors will be able to do. Most people hope that this will help to make better medicine and help sick people. Other people worry that when we learn more "words" and find out more information, we will use it in the wrong way. Just to make people more attractive , or stop sick people getting jobs. When did Mr. Mendel discover why we look the same as other people in our family? A) In 1680. B) In 1860. C) In 1953. D) In 1961.
B