The least number, which must be added to 6709 to make it exactly divisible by 9, isOptions :5378

To find the least number that must be added to 6709 to make it exactly divisible by 9, we need to find the remainder when 6709 is divided by 9.

Step 1: Divide 6709 by 9. The quotient is 745 and the remainder is 4.

Step 2: To make 6709 divisible by 9, we need to add a number that will make up for this remainder. Since the remainder is 4, we need to add 5 to 6709 to make it divisible by 9.

So, the least number that must be added to 6709 to make it exactly divisible by 9 is 5.