Let’s analyse each of the given options
- $324$
Sum of every digit $=3+2+4 = 9 =3^2$
- $441$
Sum of every digit $=4+4+1 = 9 =3^2$
- $97$
Sum of every digit $=9+7 = 16 =4^2$
- $64$
Sum of every digit $=6+4 = 10$
The sum of every digit in each these numbers $324,441,97$ is a perfect square whereas $64$ doesn’t produce sum as a perfect square.
By this logic, option D is the correct answer.
- $324=(18)^2 $
- $441=(21)^2$
- $97$ is not a perfect square of any number.
- $64=(8)^2$
By this logic, option C is the correct answer.
Hence both options C and D are correct.
As per Official answer key, both options C and D are correct.