Answer:
(C)2
Explanation:
Given the polynomial:

where x is the missing exponent.
We desire our polynomial to be a binomial (have two terms) after simplification.
We observe that the first and second term are positive and negative of almost the same term.
Therefore, we rewrite the polynomial in such a way that the first and second term cancels out.
This is:

Therefore, the missing exponent on the m in the second term is 2.