I had never seen sand dunes（沙丘）before. If you go to the seaside in Britain, you may see some small hills of sand, but nothing very impressive. Of course, Africa is home to many beautiful “sandscapes”, but I was in China, so I went to Dunhuang. I had spent my first day looking at the beautiful Mogao caves. Now I wanted to experience something very different. I have been walking in Asia, Europe and America, but nothing prepared me for walking over hills of sand. Whenever I took a step up a hill, my feet would sink into the sand and move backwards. Sometimes it seemed as if I were moving in the wrong direction. I wanted to see the sunset so I had to climb to the top of the highest sand dune. The sun was beating down upon my back as I walked slowly over the sand. Some plants had managed to survive in the dry ground but not many. As I climbed higher, the hills of sand became steeper and my feet started to slip further backwards. I ended up with my hands and knees, crawling (爬行)upwards through the top. I just let go if I would fall the way down. But I refused to give up: inch by inch, I made my way to the top of the sand dune. When I got there I was amazed by what I saw. The sand formed a very sharp point, just like a knife-edge. One side of the dune was bathed in sunshine, the other covered by shade. As I looked into the distance, the same pattern was repeated on all of the hilltops, and the difference between dark and light was beautiful. As the sun began to sink, the shadows grew longer and the light became warm and orange. The wind had come to life and sand was blown against my legs as I walked along the dunes. Soon it was getting dark and I could only just make out the line of footprints that marked my journey to the top of the hill. I slowly made my way down to the bottom, my path lit by the dying sun. 65 The author probably went to climb the sand dunes __________ after he arrived at Dunhuang. A. on the afternoon of the first day       B. on the afternoon of the second day C. on the evening of the second day     D. on the evening of the first day 66. Which of the following statements is NOT true? A. Africa has many beautiful sand dunes. B. The author could see nothing but his own footprints on his way back. C. The author had seen some kinds of sand dunes before he visited Dunhuang D. What attracted the author most was that the sand formed a very sharp point. 67. The author got to the top of the highest hill of sand _____________. A. on his hands and knees all the way B. with falls to the bottom many times C. on his hands and knees in the last leg (一段旅程) D. with a few rests all the way 68. The author mainly wants to tell readers about_____________. A. the beautiful sunset         B. his experience of climbing the sand hills C. the joy of traveling in nature  D. the difficulty of climbing the sand dunes