Ⅰ、若X→Y,则X→→Y Ⅱ、若X→→Y,则X→Y
Ⅲ、若Y í X,则X→Y Ⅳ、若Y í X,则X→→Y
Ⅴ、若X→Y,Y* ì Y,则X→Y* Ⅵ、若X→→Y,Y*ìY,则X→→Y*
A.)仅Ⅱ和Ⅳ
B.)仅Ⅰ、Ⅱ和Ⅳ
C.)仅Ⅱ和Ⅵ
D.)仅Ⅳ、Ⅴ和Ⅵ