• Dr. Smith wants to examine whether a new drug increases the maze running
performance of older rats. Just like aging humans, older rats show signs of poorer
memory for new things. Dr. Smith teaches two groups of older rats to find a
of tasty rat chow in the maze. One group of rats is given the new drug while they
are learning the maze. The second group is not given the drug. One week after
having learned the maze he retests the rats and records how long it takes them to
find the rat chow.
Independent Variable:
Dependent Variable:

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.