21．By the end of this month，the power station      for a whole year．

A．will run                   B．runs         C．has run                   D．will have run

22．Since he is angry，we        ．

A．had better leaving him alone                         B．might as well leave him alone

C．should have left him alone                            D．would rather have left him alone

23．Here we found little  snow，as most of it seemed       blown       the mountain．

A．to be；away                                              B．that it was；of

C．to have been；off                                       D．that it had been；down