Fact 1: All animals are heterotrophs.

Fact 2: Proteins are an essential nutrient for heterotrophs .

Given the two facts above, answer the question "Protein is an essential nutrient for what?" with the following options: 
- Animals
 - Algae
 - Carbohydrates
 - health
 - recovery
 - athletes
 - humans
 - Plants


 

 Animals        