Answer:
B) because the number of people who obtain flu shots is less than the socially optimal quantity
Explanation:
The reason for developing flu shot is to stop spreading of the flu and fight the illness completely. However, only a certain number of people get the shorts, and that number is less than the service needs to show the full potential of the product and to prove itself to be constructive.
The shots can be considered improvement unless enough people get them so the effects of the flu and its spreading are reduced and eventually stopped.
