Conversation so far:
Who are the Joint Chiefs of Staff and what do they do
Joint Chiefs of Staff are a panel of high-ranking U.S. military officers who advise the president of the United States and other civilian leaders on military issues.
Does the Joint Chiefs of Staff command combat and military forces
As an advisory body, the Joint Chiefs of Staff do not lead combat forces and have no executive or command authority over troops in their services.
from which u.s. military branches do the high-ranking u.s. military officers who make up the join chiefs of staff come from
The Joint Chiefs of Staff comprise the heads of the U.S. Army, Navy, Air Force, and Marine Corps.
What is the origin of the Joint Chiefs of Staff
The Joint Chiefs of Staff originated in World War II, when U.S. military leaders recognized the need for an overall command to coordinate the efforts of the various services.

Question: who appoints officers the panel
Self-contained rewrite: who appoints the high-ranking u.s. military officers in the joint chiefs of staff