Final answer:
The naturalist's argument dependence on an assumption is best represented by option 4) The Tasmanian tiger did not move and adapt to a different region in response to the loss of habitat, as it aligns with the general behavior of animals under environmental changes.
Step-by-step explanation:
An assumption is a statement that is accepted as true without proof, which forms the basis of any argument or hypothesis. Considering the options provided and the context of the naturalist's argument that factors such as habitat destruction and the behavior of animals impact their survival chance, the assumption that is critical to the argument would likely relate to the conditions that determine whether the species is still extant or not. Out of the provided options, 4) The Tasmanian tiger did not move and adapt to a different region in response to the loss of habitat is the most relevant assumption. It is based on the general understanding of animal behavior when faced with changes in their environment, as documented in the provided reference material that discusses similar patterns in other species.