20．　　　 　each other for long ， the two brothers decided to meet soon.

　 A．Not having seen　　　　　　　　　　　　　　 　　　　　　　　　　　　　　　　 B．Not seen 　　　　 　　　

　 C．Have not seen　　　　　　　　　　　　　　　　 　　　　　　　　　　　　　　　　 D．Not seeing

19．Tell John not to leave the house unless he 　　　　　that the lights ______ .

　 A．will make sure， turn off　　　　　　　　 B．makes sure; are turned off

　 C．will make sure; will turn off　　　　　　 D．makes sure; will be turned off

18．It was the training 　　　　　he had at school 　　　　　made him good jumper.

　 A．what; what 　　 B．what; that　　　 C．that; that　　 D．that; which

17．It is difficult for any of us to eat better， exercise more， and sleep enough，________ we know we should.

　 A．because　　　　　 B．even if　　　　　　　 C．unless　　　　　　　 D．before