Who names the heads of the three military departments?
d a the congress
b the president
c the secretary of defense
d the chairman of the joint chiefs

The President names the heads of the three military departments.

Option B

Explanation:

Previously, the US forces were divided into 5 branches: Coast Guard, Navy, Marine Corps, Air Force, and Army. It changed into three branches: Air force, Cavalary, and Navy. The Secretary of each defense department has control for the military and its every branch. But the country's President will be the Commander in Chief.

He will responsible for each and every final decision made in the defense department. The Secretary of Defense in each department will be appointed by the President directly by himself after a brief discussion with the Senate members.