Ace Your C++ Skills 2026 – Rock the ‘Thinking in C++’ Challenge!

An anonymous union within a class is a union that is declared without a name, similar to a struct. This can be useful for defining multiple variables together, especially when those variables might not be used at the same time. In this context, the other options are incorrect because

- Option A & B: Name and access are not the defining characteristics of an anonymous union, as these can also be present in regular unions.

- Option C: Constructors and destructors are not allowed in any type of union, anonymous or not, as unions do not have any instance-specific variables to initialize or destroy.

Hence, option D is the only option that accurately describes the special syntax required for defining an anonymous union within a class.