In an experiment, a scientist decides to study the effect of exercise on cholesterol levels in people. He studies two set of people—those who exercise every day for an hour and those who don’t exercise at all. In this case, the statement that people who exercise for an hour may have lower cholesterol levels is (blank). To test this statement, the scientist would measure cholesterol levels in exercisers and non-exercisers. The cholesterol levels would be (blank).

12) several teeth were found in an area of flat land covered with trees and plants. the teeth were examined by a paleontologist, and it was determined that the teeth came from a shark. they found many other shark teeth in this area. however, the people who discovered the teeth were puzzled, because there was no source of water near where the fossils were found. what is the paleontologist's best explanation for why the teeth were found in this area? a) sharks used to live on flat land. b) this area was once covered with salt water. c) this area was once covered with freshwater. d) someone buried the shark teeth deep in the ground.