Final answer:
The main idea of paragraph 23 is captured by the sentence about Peck informing the commander of his inability to help the sergeant, where it underlines the sergeant's role in the execution process.
Step-by-step explanation:
From the provided excerpts, which seem to detail a situation involving a sergeant and a condemned man during what appears to be an execution, the sentence that best expresses the main idea of paragraph 23 is:
c) Peck told the commander that he could not help the sergeant.
The main focus of this paragraph is on the finalization of the preparations for the execution and the doomed man’s last thoughts before a sergeant steps aside to carry out the execution order. Hence, out of the given options, this sentence encapsulates the main action taking place in paragraph 23, where the sergeant's involvement signals the impending execution.