单项选择题

设已经定义好了一个类student,现在要定义类derived,它是从student私有派生的,定义类derived的正确写法是()。

A.clasederived::studentprivate{…};
B.clasederived::studentpublic{…};
C.clasederived::privatestudent{…};
D.clasederived::publicstudent{…};