A.三個 B.二個 C.一個 D.無法確定
A.XBXb,XBY B.XbXb,XbY C.XBXb,XbY D.XbXb,XBY
A.XBXb×XBY B.XBXB×XBY C.XBXB×XbY D.XbXb×XbY