B. The connotation of the word "bright" adds to the cheerful and relieved feeling in the passage.
In these lines the troop is coming home after being away at battle. The battle is over and they have survived so there are no tense or anxious feelings as option D would suggest. Also, the description of them giving thanks to God does not suggest religious awe, but rather a sense of relief that God watched over them and they arrived home successfully. While the word "climbed" does show the toll the journey has taken on the troops, this feeling does not pervade the entire passage. Overall the words "bright", "smooth", and 'easily" all show the cheerful and relieved feeling in the passage.
