Final answer:
The author's intent is to highlight Brian's sense of isolation and helplessness in the wilderness, emphasizing his increasing concern and loneliness.
Step-by-step explanation:
The author's intent in paragraphs 12-13 of 'Hatchet' is most likely C. to emphasize Brian's increasing concern and loneliness. The repeated phrase 'He had nothing' underscores the protagonist's sense of isolation and helplessness. This emotional state is crucial for the reader to understand the gravity of Brian's situation, being alone in the wilderness without any resources. The bare, repetitive nature of the text reflects his bleak prospects and the inner turmoil he is experiencing as he grapples with the harsh reality of his circumstances. Such usage of language drives home the theme of survival against formidable odds that is central to the novel.