problem of finding Relationship in Java

Question

whats the relashon ship between these classes in java (Student class, Undergraduate class, Postgraduate class,)

Answer 1

// Possible combination
// but not if Undergraduate contains methods that should not be accessible in Postgraduate, only if they were rewritten
class Student {
String name;
}
class Undergraduate extends Student {
String thesisTopic;
}
class Postgraduate extends Undergraduate {
String doctoralThesis;
}

Answer 2

will actully that was helpful thank you for answering my Question