Fact 1: All animals are heterotrophs.

Fact 2: Proteins are an essential nutrient for heterotrophs .

Given the two facts above, answer the question "_ are an essential nutrient for animals." with the following options: 
- Energy
 - Chemicals
 - trees
 - potatoes
 - Acids
 - allow growth
 - store
 - Proteins


 

        Proteins 