Concept:Factorise a four-term expression by grouping pairs with common factors.Explanation:Rewrite the expression by rearranging terms to group useful pairs.6ax−12by−9ay+8bx=6ax−9ay+8bx−12byGroup the first two terms and the last two terms.(6ax−9ay)+(8bx−12by)Factor out the common factor from each group.3a(2x−3y)+4b(2x−3y)Now both groups contain the common binomial factor (2x−3y).Factor out (2x−3y).(3a+4b)(2x−3y)Answer:The completely factorised form is (3a+4b)(2x−3y).Therefore, the correct option is B.