Read the selection and the statements that follow. Then check the statement that you think gives the main idea most clearly. The earthworm has strong muscles under its skin and tiny bristles on its underside. When the earthworm moves, certain muscles squeeze and stretch out the front part of the body, while the rear part stays in place. Now the worm looks long and thin. The bristles on the front end stick out into the soil. Then the bristles on the rear end let go. Other muscles squeeze and pull the rear end forward while the front end stays in place. The worm now looks short and thick. The rear bristles catch the soil and the front bristles let go. The front end is stretched out again and the motions are repeated. In this way, the earthworm slowly tunnels through the soil.