The paths of glory lead ...... to the grave.

Answer: Option B

The paths of glory lead but to the grave.
In this context, the word "but" is used to convey a contrast or contradiction. The phrase suggests that despite the pursuit of glory or fame in life, ultimately, everyone meets the same fate - death. Therefore, "but" is the most appropriate choice to complete the sentence, emphasizing the inevitability of mortality despite any achievements or successes in life.