[Q]: Question: "What type of transportation system sometimes uses DC power?"  Context: "There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union."  Answer:
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[A]: railroad


[Q]: Question: "Generally speaking, if a bacteria isn't shaped like a rod, what shape would it have?"  Context: "Most bacterial species are either spherical, called cocci (sing. coccus, from Greek kókkos, grain, seed), or rod-shaped, called bacilli (sing. bacillus, from Latin baculus, stick). Elongation is associated with swimming. Some bacteria, called vibrio, are shaped like slightly curved rods or comma-shaped; others can be spiral-shaped, called spirilla, or tightly coiled, called spirochaetes. A small number of species even have tetrahedral or cuboidal shapes. More recently, some bacteria were discovered deep under Earth's crust that grow as branching filamentous types with a star-shaped cross-section. The large surface area to volume ratio of this morphology may give these bacteria an advantage in nutrient-poor environments. This wide variety of shapes is determined by the bacterial cell wall and cytoskeleton, and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators."  Answer:
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[A]: spherical


[Q]: Question: "What is the method used in Korea to sound out Chinese characters?"  Context: "Chinese character dictionaries often allow users to locate entries in several ways. Many Chinese, Japanese, and Korean dictionaries of Chinese characters list characters in radical order: characters are grouped together by radical, and radicals containing fewer strokes come before radicals containing more strokes (radical-and-stroke sorting). Under each radical, characters are listed by their total number of strokes. It is often also possible to search for characters by sound, using pinyin (in Chinese dictionaries), zhuyin (in Taiwanese dictionaries), kana (in Japanese dictionaries) or hangul (in Korean dictionaries). Most dictionaries also allow searches by total number of strokes, and individual dictionaries often allow other search methods as well."  Answer:
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[A]: hangul


[Q]: Question: "How many lines would you need to "stand still" if you were using an rpm of 78.26"  Context: "In 1925, 78.26 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor. This motor ran at 3600 rpm, such that a 46:1 gear ratio would produce 78.26 rpm. In parts of the world that used 50 Hz current, the standard was 77.92 rpm (3,000 rpm with a 77:2 ratio), which was also the speed at which a strobe disc with 77 lines would "stand still" in 50 Hz light (92 lines for 60 Hz). After World War II these records were retroactively known as 78s, to distinguish them from other newer disc record formats. Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records."  Answer:
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[A]:
92 lines