Article: Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on.

Question: What is the main example of a DC power source?
Ans: batteries


Article: The city also boasts an efficient network of public transportation, which mainly consists of bus, taxi and metro systems. The bus network, which is currently run by three companies since 2011, provides more than 370 routes covering all parts of the city and suburban areas. Nanjing Metro Line 1, started service on September 3, 2005, with 16 stations and a length of 21.72 km. Line 2 and the 24.5 km-long south extension of Line 1 officially opened to passenger service on May 28, 2010. At present, Nanjing has a metro system with a grand total of 223.6 kilometers (138.9 mi) of route and 121 stations. They are Line 1, Line 2, Line 3, Line 10, Line S1 and Line S8. The city is planning to complete a 17-line Metro and light-rail system by 2030. The expansion of the Metro network will greatly facilitate the intracity transportation and reduce the currently heavy traffic congestion.

Question: How many bus routes are there in Nanjing?
Ans: more than 370 routes


Article: During the Age of Discovery in the 15th and 16th centuries, Portugal and Spain pioneered European exploration of the globe, and in the process established large overseas empires. Envious of the great wealth these empires generated, England, France, and the Netherlands began to establish colonies and trade networks of their own in the Americas and Asia. A series of wars in the 17th and 18th centuries with the Netherlands and France left England (and then, following union between England and Scotland in 1707, Great Britain) the dominant colonial power in North America and India.

Question: In which centuries was the Age of Discovery?
Ans: 15th and 16th centuries


Article: Paragraph 6 of Article 29 stated that if a petition was successful a referendum should be held within three years. Since the deadline passed on 5 May 1958 without anything happening the Hesse state government filed a constitutional complaint with the Federal Constitutional Court in October 1958. The complaint was dismissed in July 1961 on the grounds that Article 29 had made the new delimitation of the federal territory an exclusively federal matter. At the same time, the Court reaffirmed the requirement for a territorial revision as a binding order to the relevant constitutional bodies.

Question: Paragraph 6 of Article 29 states that a referendum, in the event of a successful petition should be held within how many years?
Ans:
three