In this section you will hear several conversations. Listen to the conversations carefully and then answer the questions that follow. Questions 1 to 3 are based on the following conversation. At the end of the conversation, you will be given 15 seconds to answer the questions. Now listen to the conversation. According to the professor, why can the woman enroll in the course
A．Because it is full. B．Because it isn’t full. C．Because it is a required course for the woman. D．Because the woman has already taken Chemistry 221.