How many singers are required before the group is considered an a cappella chorus?

a. four singers total are needed.
b. the number of singers can vary.
c. there should be 8–10 singers to a part.
d. only one or two singers per part are all that is needed.

In this unit, it is mentioned that in order to enter into the field of photography, most jobs require at least a high school degree. since there is a possibility you can attain one of these jobs with just finishing high school, why do some people get an associates or bachelor’s degree?