which of the following double mutants could show synthetic genetic enhancement? select all that apply. A) Two null mutants (A, B) in genes with redundant function (A -> C, B -> C). B) Two hypomorphic mutants (A, B) in the same linear pathway (A -> B -> C). C) A constitutively-active mutant (A) and a null mutant (B) in genes with redundant function (A -> C, B -> C). D) Two null mutants (in A and B) in the same linear pathway (A -> B -> C)