GWD30-Q31

31. GWD30-Q31:

When a ton of wheat was being moved from Buffalo to New York City before the opening of the Erie Canal in 1825, it took three weeks and cost $100, but when the canal was used, it took less than eight days and cost less than $6.

A.    When a ton of wheat was being moved from Buffalo to New York City before the opening of the Erie Canal in 1825, it took three weeks and cost $100, but when the canal was used, it

It refers to a ton of wheat, illogical;

B.    Moving a ton of wheat from Buffalo to New York City before the opening of the Erie Canal in 1825, it took three weeks and cost $100; using the canal, it

It is extra here (two subjects), It cannot refer to the whole action; the second it has no referent

C.    Before the opening of the Erie Canal in 1825, moving a ton of wheat from Buffalo to New York City took three weeks and cost $100; on the canal the move

the move here clearly refers to moving a ton of wheat (both serve as a noun)

D.    In 1825, before opening the Erie Canal, to move a ton of wheat took three weeks from Buffalo to New York City, which cost $100; moving it on the canal

which cannot describe the whole sentence; it has no referent

E.     To move a ton of wheat in 1825 from Buffalo to New York City took three weeks before the opening of the Erie Canal, costing $100, but in using the canal, the move

the move here cannot refer to the action to move a ton of wheat;
                in using is awkward

感觉这题很奇怪，不知道在考点什么。反正知道D有个which肯定错；E 中costing $100 是错的。其他的不知道了。请指教