Input: IPod
The iPod has also been credited with accelerating shifts within the music industry. The iPod's popularization of digital music storage allows users to abandon listening to entire albums and instead be able to choose specific singles which hastened the end of the Album Era in popular music.

The ease of collecting singles with the iPod and iTunes is credited with ending what "era" in pop music?
Output: the Album Era

Input: United States Air Force
The fighter aircraft of the USAF are small, fast, and maneuverable military aircraft primarily used for air-to-air combat. Many of these fighters have secondary ground-attack capabilities, and some are dual-roled as fighter-bombers (e.g., the F-16 Fighting Falcon); the term "fighter" is also sometimes used colloquially for dedicated ground-attack aircraft. Other missions include interception of bombers and other fighters, reconnaissance, and patrol. The F-16 is currently used by the USAF Air Demonstration squadron, the Thunderbirds, while a small number of both man-rated and non-man-rated F-4 Phantom II are retained as QF-4 aircraft for use as Full Scale Aerial Targets (FSAT) or as part of the USAF Heritage Flight program. These extant QF-4 aircraft are being replaced in the FSAT role by early model F-16 aircraft converted to QF-16 configuration. The USAF has 2,025 fighters in service as of September 2012.

What are the QF-4 aircraft being replaced by the US Air Force? 
Output: early model F-16 aircraft converted to QF-16 configuration

Input: London
Some international railway services to Continental Europe were operated during the 20th century as boat trains, such as the Admiraal de Ruijter to Amsterdam and the Night Ferry to Paris and Brussels. The opening of the Channel Tunnel in 1994 connected London directly to the continental rail network, allowing Eurostar services to begin. Since 2007, high-speed trains link St. Pancras International with Lille, Paris, Brussels and European tourist destinations via the High Speed 1 rail link and the Channel Tunnel. The first high-speed domestic trains started in June 2009 linking Kent to London. There are plans for a second high speed line linking London to the Midlands, North West England, and Yorkshire.

In what year did the Channel Tunnel open?
Output: 1994

Input: Chicago Cubs
In June, 1998 Sammy Sosa exploded into the pursuit of Roger Maris' home run record. Sosa had 13 home runs entering the month, representing less than half of Mark McGwire's total. Sosa had his first of four multi-home run games that month on June 1, and went on to break Rudy York's record with 20 home runs in the month, a record that still stands. By the end of his historic month, the outfielder's 33 home runs tied him with Ken Griffey, Jr. and left him only four behind McGwire's 37. Sosa finished with 66 and won the NL MVP Award.

When did Sammy Sosa explode into pursuit of Roger Maris' home run record? 
Output:
1998