Problem: Anti-aircraft warfare:

The British adopted "effective ceiling", meaning the altitude at which a gun could deliver a series of shells against a moving target; this could be constrained by maximum fuse running time as well as the gun's capability. By the late 1930s the British definition was "that height at which a directly approaching target at 400 mph (=643.6 km/h) can be engaged for 20 seconds before the gun reaches 70 degrees elevation". However, effective ceiling for heavy AA guns was affected by non-ballistic factors:

Along with other factors, how long must a target be engaged to have effective ceiling?
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A: for 20 seconds

Problem: Houston:

The primary city airport is George Bush Intercontinental Airport (IAH), the tenth-busiest in the United States for total passengers, and twenty eighth-busiest worldwide. Bush Intercontinental currently ranks fourth in the United States for non-stop domestic and international service with 182 destinations. In 2006, the United States Department of Transportation named IAH the fastest-growing of the top ten airports in the United States. The Houston Air Route Traffic Control Center stands on the George Bush Intercontinental Airport grounds.

When did the U.S. Department of Transportation name IAH as fastest growing of U.S. airports?
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A: 2006

Problem: Electric motor:

Perhaps the first electric motors were simple electrostatic devices created by the Scottish monk Andrew Gordon in the 1740s. The theoretical principle behind production of mechanical force by the interactions of an electric current and a magnetic field, Ampere's force law, was discovered later by Andre-Marie Ampere in 1820. The conversion of electrical energy into mechanical energy by electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet (PM) was placed. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in physics experiments, brine substituting for toxic mercury. Though Barlow's wheel was an early refinement to this Faraday demonstration, these and similar homopolar motors were to remain unsuited to practical application until late in the century.

What toxic substance originally served the function of brine in primitive motors?
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A: mercury

Problem: Sanskrit:

The CBSE (Central Board of Secondary Education) of India, along with several other state education boards, has made Sanskrit an alternative option to the state's own official language as a second or third language choice in the schools it governs. In such schools, learning Sanskrit is an option for grades 5 to 8 (Classes V to VIII). This is true of most schools affiliated with the ICSE board, especially in those states where the official language is Hindi. Sanskrit is also taught in traditional gurukulas throughout India.

In which grades is learning Sanskrit required?
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A:
unanswerable