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.

Q: Advances were made in irrigation and farming, using new technology such as the windmill. Crops such as almonds and citrus fruit were brought to Europe through al-Andalus, and sugar cultivation was gradually adopted by the Europeans. Arab merchants dominated trade in the Indian Ocean until the arrival of the Portuguese in the 16th century. Hormuz was an important center for this trade. There was also a dense network of trade routes in the Mediterranean, along which Muslim countries traded with each other and with European powers such as Venice, Genoa and Catalonia. The Silk Road crossing Central Asia passed through Muslim states between China and Europe.

A: which crops were brought to europe from the Muslim World?
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Q: Boston has been a noted religious center from its earliest days. The Roman Catholic Archdiocese of Boston serves nearly 300 parishes and is based in the Cathedral of the Holy Cross (1875) in the South End, while the Episcopal Diocese of Massachusetts, with the Cathedral Church of St. Paul (1819) as its episcopal seat, serves just under 200 congregations. Unitarian Universalism has its headquarters on Beacon Hill. The Christian Scientists are headquartered in Back Bay at the Mother Church (1894). The oldest church in Boston is First Church in Boston, founded in 1630. King's Chapel, the city's first Anglican church, was founded in 1686 and converted to Unitarianism in 1785. Other churches include Christ Church (better known as Old North Church, 1723), the oldest church building in the city, Trinity Church (1733), Park Street Church (1809), Old South Church (1874), Jubilee Christian Church and Basilica and Shrine of Our Lady of Perpetual Help on Mission Hill (1878).

A: How long has Boston been a religious center?
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Q: The brushless wound-rotor synchronous doubly-fed (BWRSDF) machine is the only electric machine with a truly dual ported transformer circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate limited power to the rotor winding set. If a precision means were available to instantaneously control torque angle and slip for synchronous operation during motoring or generating while simultaneously providing brushless power to the rotor winding set, the active current of the BWRSDF machine would be independent of the reactive impedance of the transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond the practical capability of any other type of electric machine would be realizable. Torque bursts greater than eight times operating torque have been calculated.

A:
What is the only device with dual ported transformer circuit topology?
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