单项选择题
有Father类和Daughter类，Daughter的声明如下： class Daughter extends Father{...}则下面代码段中发生了向上转型的是（）。
A.Father f = new Daughter();
B.Daughter d = new Father();
C.Father f= new Father();
D.Daughter d = new Daughter();
单项选择题
A.Father f = new Daughter();
B.Daughter d = new Father();
C.Father f= new Father();
D.Daughter d = new Daughter();
