Fact 1: Heterotrophs are living things that cannot make their own food.

Fact 2: Proteins are an essential nutrient for heterotrophs .

Given the two facts above, answer the question "What do things that cannot make their own food need as a nutrient?" with the following options: 
- Energy
 - metal
 - animals
 - mud
 - Energy.
 - protein
 - prototype
 - fungi


 

      protein   