In an if statement, what must the code within the parentheses be?

In an if statement, the code within the parentheses must be a complete boolean expression. This is essential because the purpose of an if statement is to evaluate a condition that results in either true or false.

A complete boolean expression can include various types of comparisons, logical operators, and variables that ultimately resolve to a true or false value. For instance, expressions such as x > 5, isActive == true, or (a + b) != c all serve as valid boolean expressions that guide the flow of control in the program based on their evaluation.

The reason this option is crucial is that if the expression were just a variable, an integer expression, or a character comparison, they would not adequately express a condition that evaluates to true or false on their own. A variable alone does not guarantee that it provides a boolean value, an integer expression needs to be compared to something to create a boolean context, and a character comparison would need to be part of a larger boolean expression to determine a true or false state effectively. Thus, a complete boolean expression is necessary for the if statement to function properly and dictate the execution of subsequent code blocks.