It is D. Summer I got you!!!!!!!
That is true, enzymes are specific.
Well, I cannot see your list of suggestions but I am assuming one of them would be muscles.
Muscles use a lot of energy and require a large number of mitochondria.
1. The ability to maintain consistent conditions inside an organism, eg temperature regulation
2. The process of producing new organism with only one parent
3. The smallest unit of life, what all living things are/are made of
4. A stimulant is a change in conditions and response is how an organism reacts to the change, eg touching a hot pan and pulling your hand away
