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.

[Q]: 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 GoldwaterNichols 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?
[A]: Secretary of the Army

[Q]: Passage: In September 1828 Chopin, while still a student, visited Berlin with a family friend, zoologist Feliks Jarocki, enjoying operas directed by Gaspare Spontini and attending concerts by Carl Friedrich Zelter, Felix Mendelssohn and other celebrities. On an 1829 return trip to Berlin, he was a guest of Prince Antoni Radziwi, governor of the Grand Duchy of Posenhimself an accomplished composer and aspiring cellist. For the prince and his pianist daughter Wanda, he composed his Introduction and Polonaise brillante in C major for cello and piano, Op. 3. Question: What piece did Frederic create specifically for the prince and the prince's daughter, Wanda?
[A]: Introduction and Polonaise brillante in C major for cello and piano, Op. 3

[Q]: Passage: In 1931, RCA Victor launched the first commercially available vinyl long-playing record, marketed as program-transcription discs. These revolutionary discs were designed for playback at 33 13 rpm and pressed on a 30 cm diameter flexible plastic disc, with a duration of about ten minutes playing time per side. RCA Victor's early introduction of a long-play disc was a commercial failure for several reasons including the lack of affordable, reliable consumer playback equipment and consumer wariness during the Great Depression. Because of financial hardships that plagued the recording industry during that period (and RCA's own parched revenues), Victor's long-playing records were discontinued by early 1933. Question: Who released the first commercial long play discs?
[A]:
RCA Victor