I'm pretty sure it's both A and D, but the more correct answer is D.
Answer:
Demand increases as prices decrease.
Explanation:
You failed to provide the image of the demand curve so I will pick what a generic demand curve demonstrates.
It depends do you want to be a strictly equine vet or all around large animal vet?
I believe the answer is: Society in general.
For example, murder is considered as a criminal behavior.
Even though when a person killing another person do not directly cause damage to the whole society, the killer's existence become a threat that diminish the quality of life in that society.
