Which of the following is not true in case of public inheritance in C++?

Concept: access rules under public inheritance

When a class is derived using public inheritance, each base-class member that was public or protected keeps that same access level when referenced through the derived class. A base class's private members are different: they cannot be referenced directly by the derived class's own code under any inheritance mode (public, protected, or private) — they remain usable only within the base class's own code (and its friends).

Application: checking each statement against the rule

• A public member of the base class stays public in the derived class — this matches the rule, so it is true.

• A protected member of the base class stays protected in the derived class (usable by the derived class's own code and the base class's own friends, not by ordinary outside code) — this matches the rule, so it is true.

• A private member of the base class stays private to the base class itself — this is simply what 'private' means for the base class, independent of any inheritance; it is true.

• A private member of the base class becoming public in the derived class — this contradicts the rule, because a base class's private members cannot be referenced directly by the derived class's own code under any inheritance mode, let alone as public members.

Cross-check: the two easily-confused private-member statements

• "Remains private in the base class" describes the member staying inside its own base class — a fact about the base class alone, unrelated to inheritance, and always true.

• "Remains public in the derived class" claims the member becomes directly accessible in the derived class's own code as a public member — this is what public (and every) inheritance mode denies, since a base class's private members cannot be referenced directly by the derived class's own code, let alone as public members.

So the statement claiming that a base class's private member remains public in the derived class is the one that is NOT true — that is the statement being asked for.