Which loop is used when you are unsure how many times you may need to iterate?

The while loop is designed for situations where the number of iterations is not predetermined. It continues to execute as long as a specific condition remains true. This flexibility makes it particularly useful in scenarios where the exact number of iterations is uncertain, allowing for more dynamic control over the execution of code.

In contrast, a for loop is generally employed when the number of iterations is known beforehand, making it less suited for cases with variable repetition. A do-while loop also has a defined number of iterations controlled by a condition, but it guarantees that the loop executes at least once, which might not fit the requirement if there's a chance of not needing to execute it at all. Lastly, nested loops involve placing one loop inside another and usually assume a fixed iteration count for the outer loop, making them less adaptable for unpredictable iteration scenarios.

Thus, the while loop emerges as the appropriate choice for situations where the iteration count is uncertain, effectively assessing conditions during runtime to determine whether to continue or exit the loop.