Final answer:
Among the provided options, states do not have an obligation to deny citizens rights based on residency. This is protected under the Fourteenth Amendment and privileges and immunities clause of Article IV.
Step-by-step explanation:
The obligation that states do not have towards other states among the options outlined is (d) denying citizen rights based solely on residency. In the privileges and immunities clause of Article IV, it is outlined that states should not discriminate against citizens from other states by denying them legal protection, property rights, travel rights, and access to courts equivalent to their own citizens. However, the clause does not mean there cannot be any difference in treatment to residents and non-residents, for instance, the right to vote is restricted to residents of a state only. Furthermore, the Fourteenth Amendment guards the rights of citizens by preventing the states from denying them due process of law or equal protection under the law.
Learn more about State Obligations