Final answer:
The statement that would be relevant to the main idea of the paragraph is examples of family reunions through genealogy.
Step-by-step explanation:
The statement that would be relevant to the main idea of the paragraph is b. Examples of family reunions through genealogy. This statement directly addresses the main idea of the paragraph, which is how social networking sites have facilitated the discovery of common family roots and the reunification of separated siblings. It provides specific examples of the types of family reunions that have occurred as a result of genealogical research using social networking sites. Overall, the main idea of the paragraph is how social networking sites serve as important tools for genealogical research, connecting distant cousins and siblings who have been separated for years.