我国北方地区在农业生产中流传着这样的话：“春耕、夏种、秋收、冬藏”，你认为形成这种农业生产模式的主要影响因素是（　　）

江上渔人

江上往来人，但爱鲈鱼美。

君看一叶舟，出没风波里。​

   Mr. Li worked in a post office in Weihai. Last month he retired. His son works in America. Five years ago Mrs. Li went to America to look after their grandson. So Mr. Li decided to see them.
   Mr. Li was afraid of taking the plane so he decided to go to America by ship. On the first morning on the ship, Mr. Li met an American. The man said to him, “Good morning!” Mr. Li thought the man told him his name. So he said to him, “Li Haitao.”
   On the second morning, Mr. Li met his son’s friend on the ship. He told him about the American. After hearing that, his son’s friend laughed and said, “He said hello to you in the morning.”
   On the third morning when Mr. Li met the American again, he said, “Good morning!” And the American said to him, “Li Haitao, sir.”

下图示意的是我国正在建设中的敦煌至格尔木铁路（T），全长约506千米。据图，回答下列各题。