the answer is natural selection
C) Amino acid
because acids are the building blocks of proteins
First we have to know what an "internal stimulus" is. An "internal stimulus" is something INSIDE of us, that makes us want to do something. Hunger is an example of an internal stimulus. It comes from within us. And it makes us want to eat. So, since hunger is the stimulus, an appropriate response would be to eat some food. Does that make sense?
Answer: They contain substances/substrates in specific ways that heighten the chances of the chemicals reacting with each other
Explanation:
i took a similar quiz
C)homeostasis phenomena of adjusting to environment