听力原文：

Mr. and Mrs. Green were in a car with their three children. They were driving from Boston to Chicago. It was late at night. Mr. Green was in the front seat. He was driving the car. Mrs. Green and the children were in the back seats. They were sleeping. Mr. Green was hungry. He stopped at a fast-food restaurant. He went into the restaurant. Mrs. Green woke up. She was hungry, too. She went into the restaurant. Mrs. Green walked into the restaurant. At the same time, Mr. Green walked out of the restaurant. But he didn’t see Mrs. Green. Mr. Green drove away in the car. He drove all night. In the morning, Mr. Green and the children were in Chicago. They got out of the car. “Where is your mom?” Mr. Green asked the children. “We don’t know,” the children said. Where was Mrs. Green? She was still at the restaurant in Boston. 

答案：4. B