A scientist with mass m is sitting on one end of a lifeboat of uniform density with mass 3m. When he spots a rescue chopper in the distance, he walks a distance of L to the other side of the lifeboat to wave for help. Which of the following statements best characterizes the motion of the lifeboat? A. The lifeboat shifts by the same distance traversed, but in the opposite direction of his motion.
B. The lifeboat does not shift forward or backward as a result of the scientist's motion.
C. The lifeboat shifts by L/4 in the opposite direction of the scientist's motion.
D. The lifeboat shifts in the same direction as the scientist's motion with constant velocity.