单项选择题
A.44+XX与44+XY B.44+XX与44+YY C.22+X与22+Y D.22+XY与22+XX
A.AaXBY和AaXBXb B.AaXBY和AaXbXb C.AAXBY和AaXBXb D.AaXBY和AaXBXB
A.1/4 B.2/3 C.1/2 D.3/4