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.

[EX 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 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?
[EX A]: Secretary of the Army

[EX Q]: Passage: A series of experiments performed from the late 1800s to the early 1900s revealed that diabetes is caused by the absence of a substance normally produced by the pancreas. In 1869, Oskar Minkowski and Joseph von Mering found that diabetes could be induced in dogs by surgical removal of the pancreas. In 1921, Canadian professor Frederick Banting and his student Charles Best repeated this study, and found that injections of pancreatic extract reversed the symptoms produced by pancreas removal. Soon, the extract was demonstrated to work in people, but development of insulin therapy as a routine medical procedure was delayed by difficulties in producing the material in sufficient quantity and with reproducible purity. The researchers sought assistance from industrial collaborators at Eli Lilly and Co. based on the company's experience with large scale purification of biological materials. Chemist George Walden of Eli Lilly and Company found that careful adjustment of the pH of the extract allowed a relatively pure grade of insulin to be produced. Under pressure from Toronto University and a potential patent challenge by academic scientists who had independently developed a similar purification method, an agreement was reached for non-exclusive production of insulin by multiple companies. Prior to the discovery and widespread availability of insulin therapy the life expectancy of diabetics was only a few months. Question: Who discovered that pancreatic extract reversed symptoms of pancreas removal?
[EX A]: Frederick Banting and his student Charles Best

[EX Q]: Passage: In the beginning, racial classifications that identified race were inherently suspect and subject to strict scrutiny. These classifications would only be upheld if necessary to promote a compelling governmental interest. Later the U.S. Supreme Court decided that racial classifications that benefited underrepresented minorities were to only be upheld if necessary and promoted a compelling governmental purpose. (See Richmond v. J.A. Croson Co.) There is no clear guidance about when government action is not "compelling", and such rulings are rare. Question: Who later confirmed that racial classifications were only to be upheld if they were necessary?
[EX A]:
U.S. Supreme Court