阅读下列短文，从每题所给的四个选项 （A 、B 、C  和 D ）中，选出最佳选项。

    In 1841, a book was published which astonished the world. It was called “Incidents of Travel in Central America, Chiapas and Yucatan”. The author John Loud Stephens had just returned from a long, difficult and dangerous journey through the thick rain forest of southern Mexico and Guatemala. He had once been there with Frederick Catherwood, an architect and artist, to search for the remains of a lost civilization known as the Mayas(玛雅). Very little was known about the Mayas at that time, but Catherwood's drawing in the book showed incredible cities with temples, pyramids and other buildings as impressive as those of their northern neighbors, the Aztecs. These cities, however, were deserted. The inhabitants(居民) had disappeared almost a thousand years before.

    Since that time, far more has been learned about this remarkable civilization. The Mayas had a highly-developed system of government and of agriculture, as well as an incredibly accurate system of measuring time. They were also wonderful engineers capable of moving huge blocks stone long distances and cutting them to accurate shapes and sizes.

    And yet although the Mayas knew about the wheel, they never used it. Neither did they use metals other than copper. What is ever more surprising is that they suddenly abandoned many of their cities and built new ones in the jungle. Some time around AD 900, Mayan civilization collapsed(崩溃). By the year 1200, their last great capital, Chichen Itza, was deserted.

    Who were these strange people and the even stranger gods they worshipped? What brought about their sudden and mysterious collapse? Some writers have tried to prove that the Mayas had contact with visitors from space and even that they themselves came from another planet. Some people believe that their civilization came to an end because the Mayas never developed a proper resistance to local germs and diseases. All we really know is that when the first Europeans appeared off their coast in 1517, this great and mysterious culture was only a memory.

    Food safety is a problem in all places around the world and people in different areas of the world prepare foods in different ways. The WHO released five simple rules for preparing food in a safe way. They call these rules the “Five Keys to Safer Food”.

    Key 1: Keep clean.

          People should wash their hands often — before touching food and while they are preparing food. People should wash all surfaces and equipment used for preparing food.

    Key 2: Separate raw and cooked.

    Raw foods should not touch prepared foods.       

    Key 3:       

    People should cook eggs and meat especially carefully. These foods may carry more micro-organisms (微生物) than other foods. Food like soup must be boiled for at least a minute to make it be cooked completely. It is also important that people re-heat cooked food completely.

    Key 4: Keep food at safe temperatures.

    When people finish eating, they should keep the left food in a refrigerator below 5℃and shouldn't store it for too long. At room temperature, about 20℃, the amount of micro-organisms can increase very quickly. But temperatures above 60℃ or below 5℃ control the growth of micro-organisms.       

    Key 5: Use safe water and raw materials.

           Damaged or old food may develop harmful chemicals as it gets older.

A. Cook completely.

B. This key tells about the importance of washing.

C. Eat healthily.

D. They can live where we make food.

E. People should use safe water and choose fresh foods.

F. They cannot grow as quickly in a very hot or very cold environment.

G. People should use separate equipment and tools for touching and preparing raw foods.