Conditionals are the logic constructs used in programming to perform different actions based on whether a specified condition evaluates to true or not. Therefore, they are the correct choice for creating a block of code that should only run when a certain condition is met. Loops are used to execute a block of code repeatedly, and this does not fit the criterion of the question. While Boolean operators are used within conditionals, they are not logic constructs by themselves, but rather they work within conditionals (such as if statements) to evaluate conditions. Arithmetic operators are for performing mathematical operations and are not relevant to the question's requirement.