生命活动离不开细胞，对此理解不正确的是(　　)

   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.”