单项选择题
Questions 21 and 22 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions.
A. 13. B. 23. C. 22. D. 15.
A. It is too expensive. B. It is a bit far. C. It is too noisy. D. There is no parking space.
A. To check the accuracy of scales. B. To calculate the density of other metals. C. To observe changes in the atmosphere. D. To measure amounts of rainfall.