The writer wants to revise sentence 7 (reproduced below) to introduce the main idea of the paragraph. Which choice best accomplishes this goal? Later in the film, Obi-Wan sets up a Jedi Knight training exercise for Luke.
 1) Obi-Wan teaches Luke how to use a lightsaber.
 2) Luke discovers his true identity as a Jedi Knight.
 3) Luke learns about the Force and its power.
 4) Obi-Wan reveals the truth about Luke's father.