You are presented with the quiz "What do animals use ingestion for?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "an animal requires nutrients for survival" and "animals acquire nutrients by ingestion". So, what's the best answer to the question?

Choices:
1). Energy.
2). energy
3). reproduction
4). survival
5). excretion
6). growth
7). cooling
8). food
The answer is:
4).