International non-governmental organizations undertake a wide range of roles and tasks in global governance, including giving feedback, shaping public opinion, providing services, networking, education, norms setting, agenda setting, monitoring, and auditing. These roles increase their effectiveness, providing a perspective that differs from the official discourses of governments. Since they are considered objective, NGOs can engage with local people. International NGOs employ experts in their issue areas and operate relatively at low costs as they are based on the voluntary work of their members. The roles and impact of non-governmental organizations can be examined in three categories: shaping public opinion, contributing to international law, and providing information and documents for international organizations. Therefore, the correct option is C.