20．You should take the opportunity of hearing the　　 concert to be held in our Music

　　 Hall.

A. live　　 B．alive　　 C．1iving　 　D．1ively

19．-I’m leaving now．

　 -It’s so late．Better stay with me．Call a taxi if you　　 ．

　 A．will　　 B．must　　 C. would 　　D．may