The square root of a two-digit number gives a prime number. The sum of the two digits of such a number is equal to

Correct Answer: (B) 13

The two-digit perfect squares are 16, 25, 36, 49, 64, and 81. Among these, the square roots that are prime numbers are $\sqrt{25}=5$$\sqrt{25}$ = 5 and $\sqrt{49}=7$$\sqrt{49}$ = 7. For 25, the sum of digits is $2 + 5 = 7$ (not in options). For 49, the sum of digits is $4 + 9 = 13$, which matches option (B).