Answer:
D) He would have argued that Southern states had the right to nullify the law and residents could practice slavery unless state laws outlawed it
Step-by-step explanation:
Calhoun was an advocate for the rights of states, mainly above laws passed by the federal government. That's because he argued that the citizens of a state had the full right to vote whether they wanted a federal idol to be applied in the state or not, unless the federal government had already passed that law.
In that case, if the federal government prohibited slavery in all states, Calhoun would have argued that southern states had the right to annul the law and residents could practice slavery, unless state laws forbade it.