[SC悬赏令] prep12 Both ...and

Theauto company attributed its recent increase inprofits to both its introduction of new models in North America that areless expensive in their manufacture and to success in making its factoriesmore efficient.

(A)   to both its introduction of newmodels in North America that are less expensive in their manufacture and tosuccess in

(B)   to both its introduction of newmodels in North America that are less expensive in manufacturing and success inits

(C)   to both its introducing newmodels in North America that are less expensive in manufacturing and to successin

(D)   both to its introduction of newmodels in North America that are less expensive to manufacture and to successin

(E)    both to its introducing newmodels in North America that are less expensive in their manufacturing and tosuccess in its

这个答案是D ，但是我没看出来B错在哪里啊。both...and后面也平行啊，help~~~