Option C:
is the value of a and b
Explanation:
Given that the expression 
We need to determine the value of a and b
Let us consider the term
and take the prime factorization of the term 648
Thus, we have,
648 divides by 2,

324 divides by 2,

162 divides by 2,

81 divides by 3,

27 divides by 3,

9 divides by 3,

Thus, we have,

Therefore, equating the powers of 2 and 3, we get,

Hence, the value of a and b is 3 and 4
Thus, Option C is the correct answer.