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BeiDou-1 is an experimental regional navigation system, which consists of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese DFH-3 geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
How many satellites in the BeiDou-1 system is used for back up?
A: one

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Imperial College Boat Club
The Imperial College Boat Club was founded on 12 December 1919. The Gold medal winning GB 8+ at the 2000 Sydney Olympics had been based at Imperial College's recently refurbished boathouse and included 3 alumni of the college along with their coach Martin McElroy. The club has been highly successful, with many wins at Henley Royal Regatta including most recently in 2013 with victory in The Prince Albert Challenge Cup event. The club has been home to numerous National Squad oarsmen and women and is open to all rowers not just students of Imperial College London.
Which day was the Imperial College Boat Club formed on?
A: 12 December 1919

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Southampton used to be home to a number of ferry services to the continent, with destinations such as San Sebastian, Lisbon, Tangier and Casablanca. A ferry port was built during the 1960s. However, a number of these relocated to Portsmouth and by 1996, there were no longer any car ferries operating from Southampton with the exception of services to the Isle of Wight. The land used for Southampton Ferry Port was sold off and a retail and housing development was built on the site. The Princess Alexandra Dock was converted into a marina. Reception areas for new cars now fill the Eastern Docks where passengers, dry docks and trains used to be.
What has the Princess Alexandra Dock become?
A: a marina

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By the twentieth century, the U.S. Army had mobilized the U.S. Volunteers on four separate occasions during each of the major wars of the nineteenth century. During World War I, the "National Army" was organized to fight the conflict, replacing the concept of U.S. Volunteers. It was demobilized at the end of World War I, and was replaced by the Regular Army, the Organized Reserve Corps, and the State Militias. In the 1920s and 1930s, the "career" soldiers were known as the "Regular Army" with the "Enlisted Reserve Corps" and "Officer Reserve Corps" augmented to fill vacancies when needed.
What was added to the National Army?
A:
unanswerable