Article: Vinyl records can be warped by heat, improper storage, exposure to sunlight, or manufacturing defects such as excessively tight plastic shrinkwrap on the album cover. A small degree of warp was common, and allowing for it was part of the art of turntable and tonearm design. "wow" (once-per-revolution pitch variation) could result from warp, or from a spindle hole that was not precisely centered. Standard practice for LPs was to place the LP in a paper or plastic inner cover. This, if placed within the outer cardboard cover so that the opening was entirely within the outer cover, was said to reduce ingress of dust onto the record surface. Singles, with rare exceptions, had simple paper covers with no inner cover.

Question: What method was used to protect a vinyl record?
Ans: place the LP in a paper or plastic inner cover

Article: Of the new eastern religions introduced into the Greek world, the most successful was Christianity. From the early centuries of the Common Era, the Greeks identified as Romaioi ("Romans"), by that time the name 'Hellenes' denoted pagans. While ethnic distinctions still existed in the Roman Empire, they became secondary to religious considerations and the renewed empire used Christianity as a tool to support its cohesion and promoted a robust Roman national identity. Concurrently the secular, urban civilization of late antiquity survived in the Eastern Mediterranean along with Greco-Roman educational system, although it was from Christianity that the culture's essential values were drawn.

Question: What imperative value was extolled from the Christian community to the Roman world ?
Ans: Greco-Roman educational system, although it was from Christianity that the culture's essential values were drawn.

Article: By the 1990s Mexico City had become infamous as one of the world's most polluted cities; however the city has become a model for dramatically lowering pollution levels. By 2014 carbon monoxide pollution had dropped dramatically, while levels of sulfur dioxide and nitrogen dioxide were nearly three times lower than in 1992. The levels of signature pollutants in Mexico City are similar to those of Los Angeles.[citation needed] Despite the cleanup, the metropolitan area is still the most ozone-polluted part of the country, with ozone levels 2.5 times beyond WHO-defined safe limits.

Question: When Mexico one of the worst cities in terms of pollution?
Ans: 1990s

Article: The Delhi Flying Club, established in 1928 with two de Havilland Moth aircraft named Delhi and Roshanara, was based at Safdarjung Airport which started operations in 1929, when it was the Delhi's only airport and the second in India. The airport functioned until 2001, however in January 2002 the government closed the airport for flying activities because of security concerns following the New York attacks in September 2001. Since then, the club only carries out aircraft maintenance courses, and is used for helicopter rides to Indira Gandhi International Airport for VIP including the president and the prime minister.

Question: In what year did the government close Safdarjung Airport due to security concerns?
Ans:
2002