31．A．go                                        B．to go                             C．goes

30．A．keep                                     B．kept                              C．keeping

29．A．small                                    B．big                                C．dirty

28．A．big                                       B．bigger                           C．biggest

27．A．will have                              B．had                               C．have

26．A．thought                                B．think                          C．thinking