Fact 1: Playing is one way mammals and other animals learn how to behave.

Fact 2: Involvement in play takes time and energy.

Given the two facts above, answer the question "What is one way animals learn to behave?" with the following options: 
- garbage
 - Generating heat
 - Space travel
 - running and lifting
 - Time and energy
 - exercise
 - money
 - Riding a bike


 

     Time and energy    