1. If the rules of perspective had not been discovered, no one would have been able to paint such realistic pictures.
2. Without the new paints and the new technique, we would not be able to see the many great masterpieces for which this period is famous.
3. Among the painters who broke away from the traditional style of paining were the Impressionists，who lived and worked in Paris.
4. At the time they were created，the Impressionist paintings were controversial，but today they are accepted as the beginning of what we call "modern art".
5. You can also explore Frick's beautiful home and garden which are well worth a visit.
6. When you walk into the gallery, you feel as if you were inside a fragile, white seashell.
7. It is amazing that so many great works of art from the late 19th century to the 21st century are housed in the same museum.
8. There are various reasons why people write poetry.
9. The language is concrete but imaginative, and they delight small children because they rhyme, have strong rhythm and a lot of repetition.
10. By playing with the words in nursery rhymes, children learn about language.
11. Another simple form of poem that students can easily write is the cinquain, a poem made up of five lines.
12. With so many different forms of poetry to choose from，students may eventually want to write poems of their own.
13. I think my long and active life must be due to the healthy life I live.
14. First, you can become physically addicted to nicotine, which is one of the hundreds of chemicals in cigarettes.
15. I didn't know, for example, that it could do terrible damage to your heart and lungs or that it was more difficult for smoking couples to become pregnant.
16. It isn't easy to stop smoking, but millions have managed to quit and so can you.
17. Every time you feel like smoking a cigarette, remind yourself that you are a non-smoker.
18. It is only when the disease has progressed to AIDS that a person beginsto look sick.
19. All scientists subscribe to the view that the increase in the earth's temperature is due to the burning of fossil fuels like coal, natural gas and oil to produce energy.
20. It means that more heat energy tends to be trapped in the atmosphere causing the global temperature to go up.
21. It was a scientist called Charles Keeling, who made accurate measurements of the amount of carbon dioxide in the atmosphere from 1957 to 1997.
22. They also agree that it is the burning of more and more fossil fuels that has resulted in this increase in carbon dioxide.
23. On the other hand, there are those, like George Hambley, who are opposed to this view, believe that we should not worry about high levels of carbondioxide in the air.
24. It's OK to leave an electrical appliance on so long as you are using it — if not, turn it off!
25. Having collected and evaluated the information, I help other scientists to predict where lava from the volcano will flow next and how fast.
26. I was about to go back to sleep when suddenly my bedroom became as bright as day.
27. Having studied volcanoes now for many years, I am still amazed at their beauty as well as their potential to cause great damage.
28. The height of the land varies from 700 metres above sea level to over 2,000 metres and is home to a great persity of rare plants and animals.
29. When you arrive you are rewarded not only with the sight of its clear waters, but also by the view of the other sixteen mountain peaks that surround Tianchi.
30. It is said that this boy, who had a great gift for language and persuasion, is the father of the Manchu people.