In this section, you will hear several passages.
Listen to the passages carefully and then answer the questions that
follow.
Questions 11 to 13 are
based on. the following passage. At the end of the passage, you will be given 15
seconds to answer the questions. Now, listen to the
passage.
What is the main topic of the passage
A．The mechanics of rain. B．The climate of North America. C．How gravity affects air current. D．Types of clouds.