Final answer:
In the context of removing old finish from wood before revarnishing, the carpenter would most likely use a scraper, the correct answer being option b).
Step-by-step explanation:
The carpenter used a tool to remove the old finish from the top of the desk before revarnishing it. Among the options presented, the proper tool for removing an old finish in preparation for revarnishing would typically be a scraper. A scraper is designed to remove old paint, varnish, or stain without damaging the wood beneath, making it the ideal choice for this task. Sandpaper could also be used to smooth out the surface afterward, while a chisel would be too aggressive and a saw would not be appropriate for this purpose. Therefore, the correct answer to fill in the blank is b) scraper.