The Sierra Club runs advertisements showing how the building of a new power plant will negatively affect the air and water quality in local neighborhoods. This is an example of how interest groups can
communicate with their members
provide testimony for congressional hearings
educate the public to shape public opinion
provide specialized technical expertise to policymakers

educate the public to shape public opinion

Explanation:

An interest or pressure group is an association of individuals, organizations or sub-groups that come together to share a particular interest that could be of public concern and seek to shape government policies in favour of their interests.

Interest groups function by sensitizing the public about the danger or benefits inherent in their subject of interests. Educating the public will indirectly put pressure on the government in adjusting her policies accordingly.

Hence, running an advertisement is an example of how the public is educated in order to shape their opinion.