This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Example Input: Passage: The army is led by a civilian Secretary of the Army, who has the statutory authority to conduct all the affairs of the army under the authority, direction and control of the Secretary of Defense. The Chief of Staff of the Army, who is the highest-ranked military officer in the army, serves as the principal military adviser and executive agent for the Secretary of the Army, i.e., its service chief; and as a member of the Joint Chiefs of Staff, a body composed of the service chiefs from each of the four military services belonging to the Department of Defense who advise the President of the United States, the Secretary of Defense, and the National Security Council on operational military matters, under the guidance of the Chairman and Vice Chairman of the Joint Chiefs of Staff. In 1986, the Goldwater–Nichols Act mandated that operational control of the services follows a chain of command from the President to the Secretary of Defense directly to the unified combatant commanders, who have control of all armed forces units in their geographic or function area of responsibility. Thus, the secretaries of the military departments (and their respective service chiefs underneath them) only have the responsibility to organize, train and equip their service components. The army provides trained forces to the combatant commanders for use as directed by the Secretary of Defense. Question: Who does the Chief of Staff serve as the principal military adviser to?
Example Output: Secretary of the Army

Example Input: Passage: First recognized in 1900 by Max Planck, it was originally the proportionality constant between the minimal increment of energy, E, of a hypothetical electrically charged oscillator in a cavity that contained black body radiation, and the frequency, f, of its associated electromagnetic wave. In 1905 the value E, the minimal energy increment of a hypothetical oscillator, was theoretically associated by Einstein with a "quantum" or minimal element of the energy of the electromagnetic wave itself. The light quantum behaved in some respects as an electrically neutral particle, as opposed to an electromagnetic wave. It was eventually called the photon. Question: Who discovered an association between the value E and quantum energy?
Example Output: Einstein

Example Input: Passage: During the French Revolution, Red became a symbol of liberty and personal freedom used by the Jacobins and other more radical parties. Many of them wore a red Phrygian cap, or liberty cap, modeled after the caps worn by freed slaves in Ancient Rome. During the height of the Reign of Terror, Women wearing red caps gathered around the guillotine to celebrate each execution. They were called the "Furies of the guillotine". The guillotines used during the Reign of Terror in 1792 and 1793 were painted red, or made of red wood. During the Reign of Terror a statue of a woman titled liberty, painted red, was placed in the square in front of the guillotine. After the end of the Reign of Terror, France went back to the blue, white and red tricolor, whose red was taken from the traditional color of Saint Denis, the Christian martyr and patron saint of Paris. Question: What kind of cap did the Jacobins wear?
Example Output:
red Phrygian cap, or liberty cap

