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: In 1872, Russian Alexander Lodygin invented an incandescent light bulb and obtained a Russian patent in 1874. He used as a burner two carbon rods of diminished section in a glass receiver, hermetically sealed, and filled with nitrogen, electrically arranged so that the current could be passed to the second carbon when the first had been consumed. Later he lived in the USA, changed his name to Alexander de Lodyguine and applied and obtained patents for incandescent lamps having chromium, iridium, rhodium, ruthenium, osmium, molybdenum and tungsten filaments, and a bulb using a molybdenum filament was demonstrated at the world fair of 1900 in Paris.

SOLUTION: Who patented an incandescent light bulb in Russia in 1874?

PROBLEM: Classical India refers to the period when much of the Indian subcontinent was reunited under the Gupta Empire (c. 320–550 CE). This period has been called the Golden Age of India and was marked by extensive achievements in science, technology, engineering, art, dialectic, literature, logic, mathematics, astronomy, religion, and philosophy that crystallized the elements of what is generally known as Hindu culture. The Hindu-Arabic numerals, a positional numeral system, originated in India and was later transmitted to the West through the Arabs. Early Hindu numerals had only nine symbols, until 600 to 800 CE, when a symbol for zero was developed for the numeral system. The peace and prosperity created under leadership of Guptas enabled the pursuit of scientific and artistic endeavors in India.

SOLUTION: By what is India under the Gupta Empire referered?

PROBLEM: In 1913, Elmer McCollum discovered the first vitamins, fat-soluble vitamin A, and water-soluble vitamin B (in 1915; now known to be a complex of several water-soluble vitamins) and named vitamin C as the then-unknown substance preventing scurvy. Lafayette Mendel and Thomas Osborne also performed pioneering work on vitamins A and B. In 1919, Sir Edward Mellanby incorrectly identified rickets as a vitamin A deficiency because he could cure it in dogs with cod liver oil. In 1922, McCollum destroyed the vitamin A in cod liver oil, but found that it still cured rickets. Also in 1922, H.M. Evans and L.S. Bishop discover vitamin E as essential for rat pregnancy, originally calling it "food factor X" until 1925.

SOLUTION:
What was notable about the discovered vitamin A?