People lived on the island of Staples as far back as 19,000 BC. Man-made artifacts have been found at a number of archaeological sites. These man-made artifacts have been carbon dated to 19,000 BC. For example, a partial leg bone of a juvenile marsupial herbivore was discovered at one of the sites. This partial leg bone has been sharpened into a bone point. There is clear evidence of sharp stone tools being used to refine the bone, which were also found at the site. The fossil has no carnivore tooth marks on it and was found in a shelter on a steep escarpment unsuitable for climbing by this kind of marsupial herbivore. Only humans have the capability and dexterity to make and use these kinds of tools. This leg bone tool, therefore, was made by humans. This serves as evidence that humans lived on the island of Staples as far back as 19,000 BC. * *Fictional historical account What kind of formal reasoning is being used in this example? Check one option.