Answer:
The answer to the question: Which is an important purpose of the joint chiefs of staff, would be, B: To advuse the secretary of defense.
Step-by-step explanation
The Joint Chiefs of Staff (JCS) is a group of military leaders who work under the Department of Defense and their task is to advice not just the Secretart of Defense, but ultimately the President of the United States, Homeland Security and the National Security Council on military matters and on defense. The headquarters for the Joint Chiefs of Staff is the Pentagon and from 1986, after the Goldwater-Nichols Act, these chiefs of staff do not have operational control, as now that has been established in a downward line from the President, to the Secretary of Defense, and to the Commanders of the Combatant Command.