An earthworm is placed into a container that contains a wet paper towel on one end of a container and a dry paper towel on the other end of the container. The earthworm is placed into the center of the container and is allowed to move to either end of the container. What is the earthworm's response in this example?
a) Moves towards the wet paper towel
b) Moves towards the dry paper towel
c) Stays in the center
d) Moves randomly