The most valuable gift I have ever received was a photo album from my best friend Kevin.

      Kevin and I were classmates for all six years of primary school. We both had the same interests, so we always had a lot of things to talk about. It is wonderful to have such a good friend.

      However, last summer, Kevin had to move to another city because of his father's job. Then he gave me a photo album. “It has photos of the memorable events we have experienced together. I've also written some notes under each photo,” he said. I was deeply moved.

      I put the album beside my bed. I always look at it when I think of Kevin.

长江三角洲农耕条件优越，农业历史悠久，农业生产水平高，是举世闻名的（    ）