Concept:Use the identity p2−q2=(p−q)(p+q) to simplify the numerator.Explanation:Let p=a−b+c and q=a−b−c.Then p2−q2=(p−q)(p+q).Compute p−q=(a−b+c)−(a−b−c)=2c.Compute p+q=(a−b+c)+(a−b−c)=2a−2b.Thus numerator becomes (2c)(2a−2b).Now the expression is b−a(2c)(2a−2b).Factor 2a−2b=−2(b−a).Then b−a(2c)×(−2(b−a))=−4c.Answer:Option A: −4c