The number 729 is the square of

The correct answer is (c). 729 is the square of 27.

A square is a number multiplied by itself. For example, 9 is the square of 3, because 3 times 3 is 9.

729 is a three-digit number that is divisible by 3, 9, and 27. This means that 729 can be written as the product of three identical numbers. In other words, 729 is a perfect square.

The only perfect square among the given options is 27. Therefore, 729 is the square of 27.