In a Java application:

ClassA is an abstract class with an abstract method $m1().$

ClassB is a subclass of ClassA.

Based on this, which of the following statements are valid?

If ClassA is final, abstract method $m1()$ must have an implementation in ClassA.

ClassB can be declared final so it does not need to implement method $m1().$

If ClassB is abstract$,$ it does not need to implement method $).$

If ClassB is not abstract$,$ it must provide an implementation of method $m1().$

If ClassB is abstract$,$ method $m1()$ can be declared abstract final.