A table made entirely from the trunk of a tree said to have lived a thousand years was recently claimed to be that of a much younger tree. In order to rebut this charge, the craftsman summoned a team of dendrochronologists to prove that the tree lived to be at least to 1,000 years old. Dendrochronology, or the technique of using tree rings to date wood, is based on the fact that for each passing year a tree develops exactly one ring, as seen in a horizontal cross-section of the trunk. Given that dendrochronology is accurate for trees that lived less than 2,000 total years, the dendrochronologists will be able to determine whether the work comes from a tree that lived to be at least 1,000 years old.
Which of the following is an assumption that the argument makes?