The meanings of words can be understood through context clues. Theuse of the phrase "sullen remnant retreating" suggests
The troop’s surviving members refuse to continue the fight.
The word sullen is synonymous with resentful and moody. The use of the phrase indicates that the soldiers grew resentful because of the loss they sustained.
Because of this, they became resentful and refused to continue their fight. We know this because they began retreating.
Summarily, sentence B provides a good meaning of the phrase, "sullen remnant retreating".
