Task: Question Answering
Input (English): Which investigation might be used to demonstrate potential energy?  
 (A) Roll one ball toward another, and see what happens when they collide. (B) Place a glass of water in the freezer, and see how long the water takes to become solid. (C) Compress a spring by different amounts, and see how far it can launch a ball into the air. (D) Roll a ball from the top of an inclined plane and determine the amount of time it takes to get to the bottom.
Output (English): C