2 is CORRECT. Repeated application of the absorption theorem x + xy = x on pairs of terms in the expression gives the desired result. For example:
AB + ABC + ABCD + ABCDE + ABCDEF -------- AB + ABC = AB (x = AB, y = C) --------- AB + ABCD = AB (x = AB, y = CD) --------- AB + ABCDE = AB (x = AB, y = CDE) ----------- AB + ABCDEF = AB (x = AB, y = CDEF)