Mastering C++: A Comprehensive Quiz Based on 'Thinking in C++' 2026 - Free C++ Practice Questions and Study Guide

The operator: is the correct answer because it is the scope resolution operator, which is used to access members of a class or namespace. It is not overloadable due to safety concerns because it serves a specific purpose in determining the scope of a program, and allowing it to be overloaded could potentially create confusion or conflict within the code. The other options (operator+, operator[], operator->) are all overloadable operators and do not present the same level of safety concern.