What does an if statement do in C++?

An if statement in C++ is a fundamental control structure that allows the programmer to execute a specific block of code based on whether a certain condition evaluates to true. When an if statement is encountered, the condition within the parentheses is checked; if it evaluates to true, the block of code contained within the braces following the condition is executed. This mechanism is essential for making decisions in a program, allowing it to alter its flow of control based on varying conditions.

The other options describe actions that do not align with the function of an if statement. For example, executing code if a condition is false does not fit the purpose of an if statement, since it specifically runs code when the condition is true. Simply returning a value from a function pertains to function return statements and does not involve condition evaluation. Lastly, the concept of repeating a block of code indefinitely relates to looping structures, such as while or for loops, rather than if statements. The correct understanding of the if statement is pivotal for effectively implementing conditional logic in programming.