Questions 19 to 21 are based on the conversation you have just heard.

A．Because nine is an odd number.
B．Because the elevator got stuck.
C．Because there are too many people in the elevator.
D．Because the elevator couldn’t go to the floors above eight floor.

A．It emphasizes the importance of the communication to language learning.
B．It does not feature grammatical explanations and translation.
C．It emphasizes that students should learn English by using it.
D．It is taught exclusively in public schools.