正确答案：AB
解析：
The second part of the sentence states that travelogues do not result from relaxing travel. Therefore, the first blank indicates a word that is opposite of relaxing. (A) and (B) both imply difficulty and challenge.

(E), (F), while synonyms, are the opposite of the blank.

(C) could work in isolation, but creates a different sentence than the one that results from (A) and (B).

I suppose (D) could work in isolation, but again it creates a very different sentence than the rest of the answer choices.