题目内容：

    Death valley (死亡谷) is famous for its moving rocks. Since the early 1900s, visitors to Racetrack Playa, a dry lake bed in California have wondered how the rocks can move on their own.

These rocks leave long tracks (轨迹) behind them. The long tracks show that the rocks have moved along the ground. Those rocks only move at night and only move once every year or two. And they don’t move at the same time or in the same direction. But how do they move? How can a 350-kilogram rock move? Now scientists have known the key to the question!

Here’s how it happens.

Death Valley is one of the hottest places in the world, but it is cold at night. When it rains, the hard ground becomes soft and wet. When it gets cold enough, the water on the ground will change into very thin ice. Then the strong wind can move flat (平的) rocks along the flat ground In the morning, the sun comes up and dries the ground.

Moving rocks can be found at other places in the world as well, but Death Valley is the most famous.

1.What interests the visitors most in Death Valley?

A.The mountains around Death valley. B.The scenery of Death Valley.

C.The reason why the lake is dry. D.The secret of the moving rocks.

2.What shows the rocks can move?

A.The dry lake bed. B.The long tracks behind them.

C.The weight of the rocks. D.The shapes of the rocks.

3.How is the weather in Death Valley?

A.Hot in the day and wet at night. B.Cool in the day and dry at night.

C.Hot in the day and cold at night. D.Cold in the day and windy at night.

4.What can carry the rocks over the lake bed?

A.The wind. B.The heat. C.The rain. D.The visitors.

5.What’s the best title for this passage?

A.Dry Lake Bed B.Soft and Wet Ground

C.Tracks of Rocks D.Moving Rocks in Death Valley