GMAT Sentence Correction (SC) | Re: ing modifier doubt

To me only A makes bit sense
Hiram Bingham, explorer and professor of South American history, first crossed the Andes Mountains in February 1909,the wettest month of the year, which makes his travels difficult

making his travels difficult is a kind of verb modifier because it is used after a phrase/sentence......it sounds as if -- Hiram made his travel difficult which I don't think is the intended meaning.

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