Answer:
D, The president commands the nation's armed forces, while Congress has the power to ratify treaties
Explanation:
According to the concept of the separation of power, the government is divided into different branches with different powers that are independent of powers. The purpose of this power is to prevent the government from becoming too powerful.
In united states, those branches are divided into executive, legislative, and the judicial branches.
President is part of the executive branch. This branch has the power to execute the law, which granted it with the ability to commands nation's armed forces as long as it does not violate the law created by the legislative.
Congress is part of the legislative branch. This branch has the power to create law in the country , whether it's for domestic purpose or international purpose. This granted the congress with the power to ratify treaties.