已知

则=

  (A)        (B)               (C) 1            (D) 0

已知,,则A∩B等于

A．{x|x∈R}                              B．

C．{(0,0),(1,1)}                            D．

已知, 则=                                 (     )

   A．0          B．－4          C．－2         D．2

已知则                             

A．-4                    B．2                       C．32                   D．0

A.ab＜0                B.ab＞0                    C.ab≥0                  D.ab=0