way. I kept asking her, "When are we leaving and when are we coming back?" I asked her whether she had looked at a map yet. Of course she hadn't; my sister doesn't care about details. So I told her that the source of the Mekong is in Qinghai Province. She gave me a determined look -- the kind that said she would not change her mind. When I told her that our journey would begin at an altitude of more than 5,000 meters, she seemed to be excited about it. When I told her the air would be hard to breathe and it would be very cold, she said it would be an interesting experience. I know my sister well. Once she has made up her mind, nothing can change it. Finally, I had to give in.

　　Several months before our trip, Wang Wei and I went to the library. We found a large atlas with good maps that showed details of world geography. From the atlas we could see that the Mekong River begins in a glacier to move quickly. It becomes rapids as it passes through deep valleys, traveling across western Yunnan Province. Sometimes the river becomes a water fall and enters wide valleys. We were both surprised to learn that half of the river is in China. After it leaves China and high altitude, the Mekong becomes wide, brown and warm. As it enters Southeast Asia, its pace slows. It makes wide bends or meanders through low valleys to the plains where rice grows. At last, the river delta enters the South China Sea.

6. The text mainly tells us that the author and his sister___________.

A. plan and make preparations for their bike trip B. take a bike trip along the Mekong River

C. do some research on the Mekong River D. are fond of cycling and travelling

7. What can we learn from the text?

A. They would need others' help during their trip.

B. They knew well about the Mekong River before.

C. They gave up their trip because they would meet with many difficulties on the way.

D. Their trip would be very difficult because there would be many difficulties on the way.