A．People can call you back if necessary.
B．You can dial a special number free.
C．You don’t need to pay for a long-distance call.
D．You can get a credit coupon when you give the phone number.

A．English is the easiest language to learn.
B．English is as easy to learn as your mother tongue.
C．English can be learnt in six weeks.
D．It is easier to learn English on radio or TV.