TASK DEFINITION: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
PROBLEM: Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on.

SOLUTION: What is the largest rating of an electric motor?

PROBLEM: The timing of migration seems to be controlled primarily by changes in day length. Migrating birds navigate using celestial cues from the sun and stars, the earth's magnetic field, and probably also mental maps.

SOLUTION: What causes the timing of migration?

PROBLEM: A wide selection of serials are available from BBC Video on DVD, on sale in the United Kingdom, Australia, Canada and the United States. Every fully extant serial has been released on VHS, and BBC Worldwide continues to regularly release serials on DVD. The 2005 series is also available in its entirety on UMD for the PlayStation Portable. Eight original series serials have been released on Laserdisc and many have also been released on Betamax tape and Video 2000. One episode of Doctor Who (The Infinite Quest) was released on VCD. Only the series from 2009 onwards are available on Blu-ray, except for the 1970 story Spearhead from Space, released in July 2013. Many early releases have been re-released as special editions, with more bonus features.

SOLUTION:
What countries are the Doctor Who DVDs available to purchase?