To find the H.C.F. of the given terms, we need to factorize them first: a2bx + ab2x = abx(a + b) a2b - b2 = b(a - b) The H.C.F. of two or more terms is the product of their common factors raised to the lowest power. Both the terms have a common factor of 'b', so the H.C.F. will have 'b' as a factor. Also, the first term has a common factor of 'abx', and the second term does not have any factor of 'abx'. So, the H.C.F. will not have any factor of 'abx'. Therefore, the H.C.F. of a2bx + ab2x and a2b - b2 is 'b'. Hence, the correct answer is: b.