What functions do interest groups serve?

A special interest group (SIG) is a community within a larger organization with a shared interest in advancing a specific area of knowledge, learning or technology where members cooperate to affect or to produce solutions within their particular field, and may communicate, meet, and organize conferences.

Explanation:

An interest group is a group of people who try to affect congress's public policy on certain subjects and laws

Explanation:

do all equestions have to be answered

i think it is the third one.