Questions 11 to 18 are based on the conversation you have just heard.

A．The Hopman Cup.
B．The Masters Series.
C．The Wimbledon Championships.
D．The ATP Tour.

A．people can use their money to buy whatever they want
B．people do not need to make a complete product for exchange
C．people make a great contribution to the manufacture of a product
D．people cannot use their money to buy whatever they want