input question: Extract the answer to the question from the following context. Question: What is another name for DC motors? Context: The first commutator DC electric motor capable of turning machinery was invented by the British scientist William Sturgeon in 1832. Following Sturgeon's work, a commutator-type direct-current electric motor made with the intention of commercial use was built by the American inventor Thomas Davenport, which he patented in 1837. The motors ran at up to 600 revolutions per minute, and powered machine tools and a printing press. Due to the high cost of primary battery power, the motors were commercially unsuccessful and Davenport went bankrupt. Several inventors followed Sturgeon in the development of DC motors but all encountered the same battery power cost issues. No electricity distribution had been developed at the time. Like Sturgeon's motor, there was no practical commercial market for these motors.???
output answer: commutator-type direct-current electric motor

input question: Extract the answer to the question from the following context. Question: What part of the laser disc was most likely to cause failure of the device? Context: Many early LDs were not manufactured properly; sometimes a substandard adhesive was used to sandwich together the two sides of the disc.[citation needed] The adhesive contained impurities that were able to penetrate the lacquer seal layer and chemically attack the metalized reflective aluminium layer, causing it to oxidize and lose its reflective characteristics. This was a problem that was termed "laser rot" among LD enthusiasts, also called "color flash" internally by LaserDisc-pressing plants. Some forms of laser rot could appear as black spots that looked like mold or burned plastic which cause the disc to skip and the movie to exhibit excessive speckling noise. But, for the most part, rotted discs could actually appear perfectly fine to the naked eye.???
output answer: adhesive

input question: Extract the answer to the question from the following context. Question: In what country were there nearly 24 million students in the 1970s? Context: The economy of Russia became heavily industrialized, accounting for about two-thirds of the electricity produced in the USSR. It was, by 1961, the third largest producer of petroleum due to new discoveries in the Volga-Urals region and Siberia, trailing only the United States and Saudi Arabia. In 1974, there were 475 institutes of higher education in the republic providing education in 47 languages to some 23,941,000 students. A network of territorially-organized public-health services provided health care. After 1985, the restructuring policies of the Gorbachev administration relatively liberalised the economy, which had become stagnant since the late 1970s, with the introduction of non-state owned enterprises such as cooperatives. The effects of market policies led to the failure of many enterprises and total instability by 1990.???
output answer: Russia

input question: Extract the answer to the question from the following context. Question: Which Macedonian conqueror did not die in 298 BCE? Context: After Cassander's death in 298 BCE, however, Demetrius, who still maintained a sizable loyal army and fleet, invaded Macedon, seized the Macedonian throne (294) and conquered Thessaly and most of central Greece (293-291). He was defeated in 288 BC when Lysimachus of Thrace and Pyrrhus of Epirus invaded Macedon on two fronts, and quickly carved up the kingdom for themselves. Demetrius fled to central Greece with his mercenaries and began to build support there and in the northern Peloponnese. He once again laid siege to Athens after they turned on him, but then struck a treaty with the Athenians and Ptolemy, which allowed him to cross over to Asia minor and wage war on Lysimachus' holdings in Ionia, leaving his son Antigonus Gonatas in Greece. After initial successes, he was forced to surrender to Seleucus in 285 and later died in captivity. Lysimachus, who had seized Macedon and Thessaly for himself, was forced into war when Seleucus invaded his territories in Asia minor and was defeated and killed in 281 BCE at the Battle of Corupedium, near Sardis. Seleucus then attempted to conquer Lysimachus' European territories in Thrace and Macedon, but he was assassinated by Ptolemy Ceraunus ("the thunderbolt"), who had taken refuge at the Seleucid court and then had himself acclaimed as king of Macedon. Ptolemy was killed when Macedon was invaded by Gauls in 279, his head stuck on a spear and the country fell into anarchy. Antigonus II Gonatas invaded Thrace in the summer of 277 and defeated a large force of 18,000 Gauls. He was quickly hailed as king of Macedon and went on to rule for 35 years.???
output answer:
Demetrius