Explanation
A. The trade value of the tools 5,000 years ago is not relevant to the archaeologist's argument about the use of the tools for canoe making.
B. (Correct Response) For the archaeologist's inference to be valid, it must be assumed that the tools were present in the region 5,000 years ago. This presence would support the conclusion that the tools were used by the region's Aboriginal people at that time for making canoes. If they were transported to the region then the argument would not hold.
C. The argument does not depend on the assumption that the tools were designed exclusively for use on birch, cedar, and spruce trees, only that they were used for making canoes from these materials.
D. The argument does not necessarily assume that these were the only tools used for canoe making
5,000 years ago. The archaeologist's conclusion is about the use of these specific tools, not about the exclusivity of their use.
E. The argument does not rely on the assumption that the tools were used solely for canoe making, only that they were used for this purpose among potentially other uses.
The assumption that underpins the archaeologist's conclusion is option B. This assumption is necessary for the argument that the Aboriginal people were using these tools for canoe making at that time.