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.

[EX Q]: Most light bulbs have either clear or coated glass. The coated glass bulbs have a white powdery substance on the inside called kaolin. Kaolin, or kaolinite, is a white, chalky clay in a very fine powder form, that is blown in and electrostatically deposited on the interior of the bulb. It diffuses the light emitted from the filament, producing a more gentle and evenly distributed light. Manufacturers may add pigments to the kaolin to adjust the characteristics of the final light emitted from the bulb. Kaolin diffused bulbs are used extensively in interior lighting because of their comparatively gentle light. Other kinds of colored bulbs are also made, including the various colors used for "party bulbs", Christmas tree lights and other decorative lighting. These are created by coloring the glass with a dopant; which is often a metal like cobalt (blue) or chromium (green). Neodymium-containing glass is sometimes used to provide a more natural-appearing light.
[EX A]: What is the powdery substance in coated glass light bulbs?

[EX Q]: Up to the 1990s, the Federal District was the most populous federal entity in Mexico, but since then its population has remained stable at around 8.7 million. The growth of the city has extended beyond the limits of the Federal District to 59 municipalities of the state of Mexico and 1 in the state of Hidalgo. With a population of approximately 19.8 million inhabitants (2008), it is one of the most populous conurbations in the world. Nonetheless, the annual rate of growth of the Metropolitan Area of Mexico City is much lower than that of other large urban agglomerations in Mexico, a phenomenon most likely attributable to the environmental policy of decentralization. The net migration rate of the Federal District from 1995 to 2000 was negative.
[EX A]: How many people live in the Federal District? 

[EX Q]: In Old Chinese, (e.g. Classical Chinese) most words were monosyllabic and there was a close correspondence between characters and words. In modern Chinese (esp. Mandarin Chinese), characters do not necessarily correspond to words; indeed the majority of Chinese words today consist of two or more characters due to the merging and loss of sounds in the Chinese language over time. Rather, a character almost always corresponds to a single syllable that is also a morpheme. However, there are a few exceptions to this general correspondence, including bisyllabic morphemes (written with two characters), bimorphemic syllables (written with two characters) and cases where a single character represents a polysyllabic word or phrase.
[EX A]:
What are most words in Old Chinese?