Answer:
4. m, n
Step-by-step explanation:
Public variables are those variables that are accessible to every class or function in the program.
Private variables are variables that are accessible to only specific classes or functions in the code.
The integers i, j, m, n, z are private variables that can only be accessible to the classes in which they were declared.
For class B2, the private variables declared in it are the integers i and j. Those are the only variables that can be directly accessed by it.