Which loop guarantees at least one execution?

• A. do { /* ... */ } while (condition);
• B. while (condition) { /* ... */ }
• C. for (; condition; ) { /* ... */ }
• D. if (condition) { /* ... */ }

Answer: (A)

Post-tested loops run the body first and then check the condition, so the body is guaranteed to execute at least once. In this pattern, you execute the code inside the loop, then evaluate the condition to decide whether to continue looping. If the condition is false on the first check, you’ve already completed one execution, which is why this type of loop guarantees at least one run.

In contrast, a while loop checks the condition before any execution, so if the condition is false initially, the body may never run. A for loop with a condition behaves similarly, evaluating the condition before the first iteration and possibly skipping entirely. An if is not a loop at all; it runs its block at most once if the condition is true, but it does not repeat.