A perfect square number having n digits where n is even will have a square root with
n+1digit
n2digit
n3digit
n+12digit
Let us consider an example
36 is a perfect square and it has 2 digits
Here n=2
Hence 36=6
now 36=6 hence it has n2digit
⇒22=1
The square root of 36 is 6 which is 1, n2digit.
Hence, the option B is correct.