What method would be the best choice for a climatologist to find out what the ocean temperatures were like during the Pleistocene ice ages 30 million years ago?
1.Analyze ice core samples from pleistocene glaciers.
2.Analyze alkenones molecules of phytoplankton in rocks of that period.
3.Analyze the tree rings of petrified wood from the Pleistocene.
4.Analyze O-18 ratios from Antarctic glaciers.