Answer:
The following are visible in the main block.
1. All identifiers are visible in main
3. w (before method two)
4. z (before main)
Step-by-step explanation:
1. All the identifiers are visible in the main block because they are declared inside the class and outside the main method. By default, all identifier is declared public which make them accessible anywhere in the class except if declared within a method which give it a local scope.
3. w (before method two): w is also visible in the main method as it is also declared in the class and not within a method. Also, w is declared explicitly with the keyword public.
4. z (before main): z is also visible in the main method as it is also declared as an identifiers in the field and outside a method. Though, the variable name 'z' was overriden in the main method and reinitialized as a double.