Rivers play an important role on the earth, and we can't imagine what the earth would be like without rivers.   【小题1】

With a length of 6, 650 kilometers, the Nile is the longest river in the world. The Nile River has been the source of human civilization since ancient times. The Nile has two main branches—the White Nile and the Blue Nile. The White Nile starts from the Great Lakes region of East and Central Africa through Lake Victoria.【小题2】 The Blue Nile carries with it a lot of fertile soil which turns out to be very important to farming in Egypt.

The Amazon River is the world's largest river with a width of about 40 kilometers during the rainy seasons but about 10 kilometers wide when it is not flooded. The Amazon River has such a big water volume that it accounts for(占.....比例) more than 20% of all the world’s fresh water—far more than any other river. 【小题3】The main Amazon River flows mostly through Brazil and Peru but its tributaries can also be found in many other countries.

【小题4】It has a depth of about 250 meters. Its length is 4, 700 kilometers. The sources of the Congo River are in the highlands and mountains in the Eastern Africa Rift Valley. It's the second largest river in terms of water volume. 【小题5】The Congo River basin(盆地) is the catchments(流域，集水区) area of the Congo River. It lies in both north and south of the Equator, making its flow very stable as there are always some tributaries experiencing a rainy season at any time.

Some Deep Lakes in the World

Lake Tanganyika (4710 feet)

Lake Tanganyika is the second largest freshwater(淡水的) lake in the world and the second deepest lake of any kind. It sits on the border between Zambia, Burundi, Tanzania, and the Democratic Republic of the Congo. Since the Stone Age, human communities on the shores of the lake have fed themselves by fishing there.

Caspian Sea (3360 feet)

The Caspian Sea, which lies between the Caucasus Mountains and the Central Asian Steppe, is the largest fully enclosed body of water on earth and the world’s largest salt lake. Commercial fishing and tourism to the Caspian shore play an important role in the economies of the surrounding countries.

Lake Nyasa(2316 feet)

Lake Nyasa is a long thin lake, stretching more than 350 miles along the borders between Mozambique, Tanzania, and Malawi. Because its length, depth, and temperature stratification(分层) create a number of completely different environments, Lake Nyasa has an extremely high level of biodiversity.

Lake Baikal(5315 feet)

Lake Baikal, in Siberia, holds the distinction of being both the deepest lake in the world and the largest freshwater lake, holding more than 20% of the unfrozen fresh water on the surface of earth. It is also the oldest freshwater lake in the world, with an estimated age of 20 million to 25 million years.

Lake Vostok (2950 feet)

Lake Vostok, in Antarctica, is unique among the lakes in that it is buried under nearly 2.s miles of ice. It is the largest known subglacial(冰川底部的) lake.

They say that Mexico is a country no one ever leaves. Every year, millions of tourists pass through, and Mexicans happily warn that a part of them will remain behind forever. Most visitors are vacationing North Americans who end up on the brilliant beaches of Cancun, Acapulco, Mazatlan, and Puerto Vallarta. The beaches, of course, are among the world’s best – but those who venture inland are rewarded with the true soul of Mexico.

And it is a big soul. The Republic of Mexico is vast, consisting of nearly two million square miles of coastline, desert, rain forest, mountains and fertile plains. From the American borderlands of the wide, agriculturally rich north, the country narrows gently as it sweeps south and east. The two main mountain ranges, the Sierra Madre Occidental and the Sierra Madre Oriental, hug the west and east, finally merging into the volcanically active central highlands and the capital, Mexico City – the most populous city in the world. Further south, the country narrows to only 100 miles, then broadens again before reaching the Guatemalan border. There are two major peninsulas (半岛) in Mexico: the Baja Peninsula to the west and the Yucatan peninsula to the east.

The population is about 106 million, and the generosity (宽宏大量的) of the Mexican people is unsurpassed. Knowing a few simple sentences in Spanish will win hearts.

Mexico has been graced with an unusually temperate climate all year round. The most important thing to remember is that the Mexican summer is also the rainy season, although the rain rarely lasts more than a few hours, and typically arrives in the late afternoon. Extremes are present only in the north and in Baja, both of which have deserts where the temperature leaps above 100℉. Mexico City has a year-round temperature in the high 80s, while the coasts usually stay in the mid-90s. Night time temperatures fall somewhat, but rarely break down below a comfortable 60℉.