2 . The Lake on Top of a Mountain

Imagine a lake as blue as the summer sky, surrounded by thousands of pine trees and towering mountains.    1    , but Lake Tahoe is a real place in the Sierra Nevada Mountains, along the border of California and Nevada.

People come during every season to enjoy Lake Tahoe. It is the perfect spot for camping, boating, fishing, biking, and hiking.    2    . Most of the small towns surrounding Lake Tahoe have lodge(集会处)where families can go to ski or snowboard. These holiday destinations are much more fun to stay at than the ones in other parts of the country.

    3    , but the area was popular long before California and Nevada were even states. Native Americans from the Washoe tribe(部落)traveled through the mountains and spent their summers at Lake Tahoe. In fact, the name Tahoe comes from a Washoe and meaning "big water". The Washoe were expert hunters who used the land and water for their food supply.    4    . The best one is about very large birdlike monster(怪物)that lived in the middle of the lake and ate people!

While people now use Lake Tahoe mostly for fun rather than survival, it is still important to keep the water and land clean. California and Nevada work together to make sure these natural resources are used wisely.    5    . There would be no place as beautiful or fun for a vacation as Lake Tahoe.

Yellow River Valley is the birthplace of ancient Chinese     1    （civilize）, and for that reason the Yellow River is often called "Mother River." The valley     2    （surround）the principal river of northern China and is at the center of thousands of years of Chinese history. It is called the Yellow River     3     its waters carry soil, which gives the river     4    （it）yellow-brown color, and when the river overflows, it leaves a yellow residue（残留）behind. While the river helps create fertile land that is suitable     5     farming, during certain times of the year the Yellow River frequently overflows. The water damages     6    （house）and crops across the North China Plain, an important     7    （agriculture）region. For thousands of years, the Chinese have carried out major public work projects     8    （control）the water from the Yellow River. Despite the possibility of flooding, many of China's cities,     9    （situate）along the river, are growing increasingly in the valley,     10     have become the center of Chinese culture, society, and learning.