Which sentence from the passage reveals the author's point of view?
A. This design allows the train to change its energy between potential and kinetic energy until friction eventually causes the energy reservoir built by the lift hill to be entirely spent.
B. Those who love to ride a roller coaster can look forward to even greater thrills with increased speed, height, and gravitational forces.
C. This sensation can also cause "butterflies" in the stomach as the body senses the increased speed.
D. At the top of the next smaller hill, the energy of the train changes from kinetic energy back to potential energy, and the ride continues.
