Correct option is C
Perform the prime factorization: 28 = 22.7 For a number to be a perfect square, all prime factors must have even powers.
28 = 22.7
The power of 2 is already even (22).
The power of 7 is odd (71). To make 28 a perfect square, the power of 7 must also be even.
Multiply 28 by 7:
28⋅7 = 196 = 22.72
The least number which when multiplied by 28 forms a perfect square is 7.
