Your Answer is

Correct Answer is G

Explanation

For this kind of problem, you need to consider the marginal value, that is, test the maximum 3 digits (999), the minimum three digits (100), the maximum two digits (99), the minimum two digits (10), etc.

It is known that this perfect square number has 4 digits, then the square of the number after the root sign is still this perfect square number. For any 2-digit number, the square interval is between (10²,992), that is, from 3 digits to 4 digits, and for any 3-digit number, the square interval is (100 ²,999²), that is, from 5 digits to 6 digits. Then it can be determined that the positive integer root of this 4-digit perfect square number is 2 digits. The answer is G.