Why can I access the private members of an enclosing class reference

Question

I have seen many questions about accessing private members of an enclosing class. However, my question is the opposite.

If I have (as an example), the following cod

Answer 1

B is a member of A and therefore has access to A's private fields and methods.
In this case, although B is static it is using an instance of A to access the field A.outerString.