Question

how do animals obtain the nitrogen they use to make proteins and nucleic acids?

by absorbing ammonia from bacteria growing in the roots of plants

by consuming plants or other animals

by breathing the nitrogen present in the atmosphere

by absorbing nitrogen found in the soil

Explanation:

Animals cannot fix atmospheric nitrogen, absorb soil nitrogen directly, or take ammonia from root bacteria. They rely on consuming organic nitrogen sources: plants (which have fixed nitrogen via bacteria) or other animals that have already obtained nitrogen from plants.

Answer:

by consuming plants or other animals