Concept:Group terms to form a common binomial factor.Explanation:Rewrite the expression by grouping like terms.am+bn−an−bm=am−an−bm+bnFactor each pair:=a(m−n)−b(m−n)Now take out the common factor (m−n):=(a−b)(m−n)Answer:(a−b)(m−n)Correct option: B. (a−b)(m−n)