To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) It must be marked final - This option is incorrect. Method-local inner classes do not have any restrictions on being marked as final. They can be marked as final, but it is not a requirement.
Option B) It can be marked abstract - This option is correct. Method-local inner classes can be marked as abstract. This allows the class to have abstract methods that must be implemented by any non-abstract subclasses.
Option C) It can be marked public - This option is incorrect. Method-local inner classes cannot be marked as public. They can only have either default (package-private) or private access modifiers.
Option D) It can be marked static - This option is incorrect. Method-local inner classes cannot be marked as static. They are implicitly associated with an instance of the enclosing class and cannot exist without an instance of the enclosing class.
Therefore, the correct answer is B) It can be marked abstract. This option is correct because method-local inner classes can be marked as abstract and have abstract methods.
Please select the most appropriate option.