Final answer:
This provision allows Congress to organize and control the militia while it is in national service, but states retain the power to appoint officers and train the militia as prescribed by Congress. The correct option is 1.
Step-by-step explanation:
The provision in question is meant to outline the distribution of powers between the federal government and the states regarding the militia, which today is known as the National Guard.
The purpose is multi-faceted: It serves to ensure a structured military force that can be called upon for national defense, while also preserving the states' authority to appoint officers and train the militia.
Specifically, the provision allows Congress to organize, arm, and discipline the militia, and to govern the part that may be employed in the service of the United States.
However, it reserves to the states the appointment of officers and the authority to train the militia under the discipline prescribed by Congress. The correct option is 1