Art restorers who have been studying the factors that cause Renaissance oil paintings to deteriorate physically when subject to climatic changes have found that the oil paint used in these paintings actually adjusts to these changes well. The restorers ttherefore hypothesize that it is a layer of material called gesso, which is under the paint, that causes the deterioration.
The statement 'Renaissance oil paintings with a thin layer of gesso are less likely to show deterioration in response to climatic changes than those with a thicker layer' most strongly supports the restorers' hypothesis.