Step 1: Understanding the Question
The question asks for the reason why men would flee to the forest.
Step 2: Locating the Information in the Passage
We should look for keywords like "run away" and "forest".
The fourth sentence states: "Often when a man feared some punishment from the Sheriff, he would run away to the forest."
The passage later mentions that once in the forest, these men (outlaws) would hunt deer and rob travellers to survive, but that was not the initial reason for running away.
Step 3: Analyzing the Options
(A) Joining the army is not mentioned as a reason.
(B) Hunting deer was a means of survival in the forest, not the reason for going there.
(C) Robbing travellers was also a means of survival, not the primary reason for fleeing.
(D) Escaping punishment from the Sheriff is the exact reason given in the passage.
Step 4: Final Answer
The passage directly links running away to the forest with the fear of punishment from the Sheriff. Thus, option (D) is correct.