Final answer:
A not-for-profit organization receiving support mainly from a few sources and focusing on granting funds to public charities is called a Private foundation.
Step-by-step explanation:
A not-for-profit organization that is exempt from federal income taxes under IRC Sec. 501(c)(3), exists to make grants to public charities, and receives its support from a small number of individuals or corporations and investment income rather than from the public at large is called a: b) Private foundation.
Non-profit organizations include entities such as welfare groups, churches, hospitals, schools, museums, civic organizations, fraternal organizations, veterans organizations, and social clubs. These are typically structured similarly to corporations but are established to serve a public or mutual benefit other than the pursuit of profits. A private foundation is a type of non-profit organization which typically receives its money from a single primary source like a family or corporation and uses those funds to make grants to other charities or engage in direct charitable activities.