Language points

2. Almost all of them occur in the US, in the area from Texas in the southeast to South Dakota in the north. occur:发生=happen 他告诉我那事故是怎样发生的. He told me how the accident occurred. occur to(想法念头等)想起,浮现 今天早上起床时,我突然想到了一个好主意. An excellent idea occurred to me when I woke up this morning. 我突然想到要到欧洲旅游. It occurred to me that I would travel to Europe.