A.三個(gè) B.二個(gè) C.一個(gè) D.無(wú)法確定
A.XBXb,XBY B.XbXb,XbY C.XBXb,XbY D.XbXb,XBY
A.XBXb×XBY B.XBXB×XBY C.XBXB×XbY D.XbXb×XbY