21．People，especially teens，think it___________great fun to surf on___________Internet.
A．不填；the B．a；不填 C．a；the D．不填；不填
22．--We could invite John and Barbara to the Friday night party．
--Yes，_____________? I,ll give them a call right now．
A．why B．what for C．why not D．what
23．I walked up to the top of the hill with my friend，______we enjoyed a splendid view of the
lake．
A．where B．which C．who D．that
