TASK DEFINITION: In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.
PROBLEM: Question: Which form of energy is produced when paper is burned? Answer: heat

SOLUTION: Heat is produced when paper is burned.

PROBLEM: Question: Corals build hard exoskeletons that grow to become what? Answer: coral reefs

SOLUTION: Corals build hard exoskeletons that grow to become coral reefs.

PROBLEM: Question: In harmonic motion there is always what force, which acts in the opposite direction of the velocity? Answer: restorative force

SOLUTION:
In harmonic motion there is always restorative force force, which acts in the opposite direction of the velocity.