The correct answer is option C: This evidence supports the argument by giving an example of a library service that has a positive impact upon specific residents of the community.
The Bookmobile service provides the opportunity to "reach a library" to a specific group of residents of the community: "disadvantaged children and migrant workers on the city's west side, as well as many senior citizens in nursing homes". This service has a positive impact on that group of people since it is a way in which they can have access to the library services.