Input: Article: Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

Now answer this question: Why is DC motor being used more than AC type?

Output: conversion was not well developed

Input: Article: The northwestern portion of Rajasthan is generally sandy and dry. Most of this region are covered by the Thar Desert which extends into adjoining portions of Pakistan. The Aravalli Range does not intercept the moisture-giving southwest monsoon winds off the Arabian Sea, as it lies in a direction parallel to that of the coming monsoon winds, leaving the northwestern region in a rain shadow. The Thar Desert is thinly populated; the town of Jodhpur is the largest city in the desert and known as the gateway of thar desert. The desert has some major districts like Jodhpur, Jaisalmer, Barmer, Bikaner and Nagour. This area is also important defence point of view. Jodhpur airbase is Indias largest airbase and military, BSF bases are also situated here. A single civil airport is also situated in Jodhpur. The Northwestern thorn scrub forests lie in a band around the Thar Desert, between the desert and the Aravallis. This region receives less than 400 mm of rain in an average year. Temperatures can exceed 48 °C in the summer months and drop below freezing in the winter. The Godwar, Marwar, and Shekhawati regions lie in the thorn scrub forest zone, along with the city of Jodhpur. The Luni River and its tributaries are the major river system of Godwar and Marwar regions, draining the western slopes of the Aravallis and emptying southwest into the great Rann of Kutch wetland in neighboring Gujarat. This river is saline in the lower reaches and remains potable only up to Balotara in Barmer district. The Ghaggar River, which originates in Haryana, is an intermittent stream that disappears into the sands of the Thar Desert in the northern corner of the state and is seen as a remnant of the primitive Saraswati river.

Now answer this question: Dry and sandy conditions are indicative of which region of Rajasthan? 

Output: The northwestern portion

Input: Article: Hydrogen was liquefied for the first time by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask. He produced solid hydrogen the next year. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932. François Isaac de Rivaz built the first de Rivaz engine, an internal combustion engine powered by a mixture of hydrogen and oxygen in 1806. Edward Daniel Clarke invented the hydrogen gas blowpipe in 1819. The Döbereiner's lamp and limelight were invented in 1823.

Now answer this question: Who was the first to discover deuterium?

Output:
Harold Urey