As commander in chief, the leads the armed forces.

As commander in chief, the President of the United States leads the Armed Forces.

Explanation:

The United States Armed Forces are formed by: the Navy, the Marine Corps, the Coast Guard, the Air Force and the Army. All the forces are part of the uniformed services of the United States and are under the civilian control of the President of the United States, who acts as Commander-in-Chief.  But the President can never declare war, since that power belongs to Congress.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain

c or d both can be the answer