Input: Read this: Solar energy may be used in a water stabilisation pond to treat waste water without chemicals or electricity. A further environmental advantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although algae may produce toxic chemicals that make the water unusable.
Question: What is a reason why the water from a water stabilisation pond may be unusable?

Output: algae may produce toxic chemicals


Input: Read this: Standard 35mm photographic film used for cinema projection has a much higher image resolution than HDTV systems, and is exposed and projected at a rate of 24 frames per second (frame/s). To be shown on standard television, in PAL-system countries, cinema film is scanned at the TV rate of 25 frame/s, causing a speedup of 4.1 percent, which is generally considered acceptable. In NTSC-system countries, the TV scan rate of 30 frame/s would cause a perceptible speedup if the same were attempted, and the necessary correction is performed by a technique called 3:2 Pulldown: Over each successive pair of film frames, one is held for three video fields (1/20 of a second) and the next is held for two video fields (1/30 of a second), giving a total time for the two frames of 1/12 of a second and thus achieving the correct average film frame rate.
Question:  The 3:2 Pulldown techniques gives what total time for five frames?

Output: unanswerable


Input: Read this: Between the German invasion of Poland on 1 September 1939 and the Anglo-French declaration of War against the German Reich on 3 September 1939, the entire city (a total of 120,000 people) was evacuated, like other border towns as well. Until the arrival of the Wehrmacht troops mid-June 1940, the city was, for ten months, completely empty, with the exception of the garrisoned soldiers. The Jews of Strasbourg had been evacuated to Périgueux and Limoges, the University had been evacuated to Clermont-Ferrand.
Question: How many garrisoned soldiers were left in Strasbourg?

Output: unanswerable


Input: Read this: Cartooning is most frequently used in making comics, traditionally using ink (especially India ink) with dip pens or ink brushes; mixed media and digital technology have become common. Cartooning techniques such as motion lines and abstract symbols are often employed.
Question: Motion lines and what are never used in comics?

Output:
unanswerable