10 free GMAT practice questions in the real exam format, covering the official content areas, with an explanation for every answer.
GMAT Practice Test 6Tutor mode
Question 1 of 10
Verbal Reasoning
At a site in a dry river valley, grinding stones occur in every layer of deposits, from the oldest to the most recent. Residue of wild barley, however, appears only on stones in layers dated to about 9,000 years ago or later. Archaeologists conclude that the site's inhabitants began processing barley only about 9,000 years ago.
Which of the following, if true, most strengthens the archaeologists' conclusion?