When can sentence fragments actually make a piece of writing MORE effective? in a descriptive passage in a novel
in a concluding paragraph of an essay
during dialogue in a novel
in an introductory paragraph of an essay

London includes a quote about john thornton as he is observing hal attempt to motivate the exhausted dogs "it was idle, he knew, to get between a fool and his folly". if the word "idle" is defined as "of no real worth, importance, or significance", what does this statement mean with regard to hal? who is the fool? what is hal's folly? why would john thornton think it of no real worth or useless to intervene?