What Is the Primary Purpose for the President's Designation as Commander-In-Chief

What is the primary purpose for the president's designation as commander-in-chief?

A) to use the military experience that presidents must have for leading troops into battle
B) to allow for the United States to have the ability to declare war and take necessary military action
C) to allow the military to ultimately remain under civilian control
D) to simplify the chain of command
E) to improve relationships and alliances with the military in other nations