Final answer:
State Governments have the primary responsibility for defining marriages and other civil contracts, but must adhere to federal rulings such as the 14th Amendment and the Supreme Court's decision in Obergefell v. Hodges, reflecting the interplay of state and federal jurisdiction.
Step-by-step explanation:
The primary responsibility for defining marriages and other civil contracts lies with b) State Government. In the United States, the individual state governments have the authority to regulate marriage, which is a component of their reserved powers to oversee matters of health, safety, morality, and welfare of their citizens.
The 14th Amendment and the Supreme Court's decision in Obergefell v. Hodges further clarify that states must recognize marriage as a fundamental right, thus ensuring that same-sex couples have the right to marry.
However, it's important to note that while states have the primary responsibility for these regulations, certain aspects of marriage law, especially those concerning the rights of LGBTQ people, have become intertwined with federal policies, highlighting the dynamic nature of federalism in the United States.