Butler is a wild mushroom that grows under host trees that provide it with the sugar it needs, such as Douglas fir. In turn, Butler's underground rhizome filaments can break down these sugars and provide their hosts with Nutrient and moisture. It is because of this reciprocal relationship that the pickle growing under the cut Douglas fir will cause serious damage to this tree. Which of the following judgments, if correct, raises the strongest doubt about the above conclusions? ['Douglas fir is not a precious rare tree.', 'Butler grows not only under Douglas fir trees, but also under other host trees.', 'Other wild mushrooms also grow under Douglas fir trees, and have similar characteristics to Butler.', 'The harvest of wild mushrooms has stimulated its growth.']