SECTION A CONVERSATIONS In this section you will hear several conversations. Listen to the conversations carefully and then answer the questions that follow. Questions 1 to 4 are based on the following conversation. At the end of the conversation, you will be given 20 seconds to answer the questions.
Now listen to the conversation. What is the purpose of this class discussion
A．To discuss the results of the lab experiment. B．To answer Bob’s question about the lab experiment. C．To explain the method of collection by water displacement. D．To prepare the students to do the lab experiment.