A program should continue receiving an input number and outputting that number squared until the input number is negative. Which control structure should be used?

A for loop is typically used when the number of iterations is known in advance, such as iterating over a fixed range or a collection. Since the requirement here is to continue processing until a negative input is received—an indeterminate number of iterations—a for loop is not suitable for this task.

An if statement is a conditional structure that executes a block of code only once if the condition is true. It does not facilitate repeated execution based on a condition, which is necessary for continuously processing input. Therefore, it cannot fulfill the requirement of responding to ongoing input until a negative number is encountered.

While multiple if statements can handle various conditions, they still do not provide a looping mechanism to repeatedly execute code. This means they cannot effectively manage continuous input and output in the manner required by the prompt. Each if statement would only execute once, failing to meet the requirement for an indefinite number of iterations.