Final answer:
None of the provided options accurately explain why Francois weeped over Buck. Instead, his weeping over Buck might be attributed to a deep emotional bond, but this is not directly taken from "The Call of the Wild." The correct answer is none of the above.
Step-by-step explanation:
In determining why Francois wept over Buck, one must understand the context provided by Jack London in his novel "The Call of the Wild." This reference to Francois does not directly correspond to an event in London's story. However, based on our knowledge of the narrative, Buck's compelling story included moments where he dealt with sickness, adversity, and changes in ownership, which could have led someone like Francois, a character in the book, to weep for him
Nevertheless, to specifically answer why Francois weeped over Buck, none of the given options - A. Buck being killed by another dog, B. Buck breaking his leg and could no longer work, C. Buck being very sick, or D. Buck was sold to a new owner - are accurate. Instead, Buck's ultimate transformation and his induction into a wolf pack might cause a character like Francois deep emotion.
Therefore, the correct option that best explains a potential reason for Francois's emotional reaction to Buck's circumstances would be the deep bond and affection he had developed for Buck. Regardless, it's important to note that the options given do not accurately reflect any specific passage from "The Call of the Wild."