The problem: Answer a question about this article:
Replicated CDs are mass-produced initially using a hydraulic press. Small granules of heated raw polycarbonate plastic are fed into the press. A screw forces the liquefied plastic into the mold cavity. The mold closes with a metal stamper in contact with the disc surface. The plastic is allowed to cool and harden. Once opened, the disc substrate is removed from the mold by a robotic arm, and a 15 mm diameter center hole (called a stacking ring) is created. The time it takes to "stamp" one CD is usually two to three seconds.
What is the term for the center hole in a CD?
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The answer: stacking ring

The problem: Answer a question about this article:
The BCG vaccine has limitations, and research to develop new TB vaccines is ongoing. A number of potential candidates are currently in phase I and II clinical trials. Two main approaches are being used to attempt to improve the efficacy of available vaccines. One approach involves adding a subunit vaccine to BCG, while the other strategy is attempting to create new and better live vaccines. MVA85A, an example of a subunit vaccine, currently in trials in South Africa, is based on a genetically modified vaccinia virus. Vaccines are hoped to play a significant role in treatment of both latent and active disease.
What does one option propose adding to the existing BCG vaccine?
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The answer: subunit vaccine

The problem: Answer a question about this article:
In 2003, a congestion charge was introduced to reduce traffic volumes in the city centre. With a few exceptions, motorists are required to pay 10 per day to drive within a defined zone encompassing much of central London. Motorists who are residents of the defined zone can buy a greatly reduced season pass. London government initially expected the Congestion Charge Zone to increase daily peak period Underground and bus users by 20,000 people, reduce road traffic by 10 to 15 per cent, increase traffic speeds by 10 to 15 per cent, and reduce queues by 20 to 30 per cent. Over the course of several years, the average number of cars entering the centre of London on a weekday was reduced from 195,000 to 125,000 cars a 35-per-cent reduction of vehicles driven per day.
What is the daily cost for most drivers to operate their cars within a given zone in the center of London?
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The answer: 10

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Indira Gandhi International Airport, situated to the southwest of Delhi, is the main gateway for the city's domestic and international civilian air traffic. In 2012-13, the airport was used by more than 35 million passengers, making it one of the busiest airports in South Asia. Terminal 3, which cost 96.8 billion (US$1.4 billion) to construct between 2007 and 2010, handles an additional 37 million passengers annually.
Approximately how many passengers used Indira Gandhi Airport from 2012-2013?
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The answer:
35 million