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: In New York City in 1846, Alexander Turney Stewart established the "Marble Palace" on Broadway, between Chambers and Reade streets. He offered European retail merchandise at fixed prices on a variety of dry goods, and advertised a policy of providing "free entrance" to all potential customers. Though it was clad in white marble to look like a Renaissance palazzo, the building's cast iron construction permitted large plate glass windows that permitted major seasonal displays, especially in the Christmas shopping season. In 1862, Stewart built a new store on a full city block with eight floors and nineteen departments of dress goods and furnishing materials, carpets, glass and china, toys and sports equipment, ranged around a central glass-covered court. His innovations included buying from manufacturers for cash and in large quantities, keeping his markup small and prices low, truthful presentation of merchandise, the one-price policy (so there was no haggling), simple merchandise returns and cash refund policy, selling for cash and not credit, buyers who searched worldwide for quality merchandise, departmentalization, vertical and horizontal integration, volume sales, and free services for customers such as waiting rooms and free delivery of purchases. His innovations were quickly copied by other department stores. Question: What policy did the Marble Palace introduce? 
[EX A]: "free entrance" to all potential customers.

[EX Q]: Passage: Philadelphia has more public art than any other American city. In 1872, the Association for Public Art (formerly the Fairmount Park Art Association) was created, the first private association in the United States dedicated to integrating public art and urban planning. In 1959, lobbying by the Artists Equity Association helped create the Percent for Art ordinance, the first for a U.S. city. The program, which has funded more than 200 pieces of public art, is administered by the Philadelphia Office of Arts and Culture, the city's art agency. Question: Which American city has the most public art?
[EX A]: Philadelphia

[EX Q]: Passage: Air defence in naval tactics, especially within a carrier group, is often built around a system of concentric layers with the aircraft carrier at the centre. The outer layer will usually be provided by the carrier's aircraft, specifically its AEW&C aircraft combined with the CAP. If an attacker is able to penetrate this layer, then the next layers would come from the surface-to-air missiles carried by the carrier's escorts; the area-defence missiles, such as the RIM-67 Standard, with a range of up to 100 nmi, and the point-defence missiles, like the RIM-162 ESSM, with a range of up to 30 nmi. Finally, virtually every modern warship will be fitted with small-calibre guns, including a CIWS, which is usually a radar-controlled Gatling gun of between 20mm and 30mm calibre capable of firing several thousand rounds per minute. Question: What protects the outer layer?
[EX A]:
AEW&C aircraft combined with the CAP