DYNAMITE
In recent years, troubled airlines have exchanged their aging, inefficient fleets for a smaller number of efficient new airplanes,
in part because high fuel costs should be lowered and repair costs should be reduced and partly because low entry barriers for new carriers have created intense competition.
(A) in part because high fuel costs should be lowered and repair costs should be reduced
should be usage twice is redudant in addition in part isn't delivering the right meaning therefore out
(B) in part that high fuel costs might be lowered and repair costs might be reduced
might be lowered isn't the intended objective , the airline is going all out to reduce the expenses therefore out
(C) partly because high fuel costs should be lowered and repair costs should be reduced
partly and because usage together is redudant therefore out
(D) partly for the lowering of high fuel costs and the reduction of repair costs
lowering isn't parallel with reduction therefore out
(E) partly to lower high fuel prices and reduce repair costs
The meaning is perfect therefore our answer
Therefore IMO E