单项选择题
Questions 19 to 22 are based on the conversation you havejust heard.
A. 800 years. B. 400 years. C. 550 years. D. 2,000 years.
A. 80 million. B. 70 million. C. More than 3,500 million. D. About 3,000 million.
A. Classmates. B. Boss and secretary. C. Husband and wife. D. Teacher and student.