Problem: Please answer a question about the following article about Antenna (radio):
A Yagi-Uda array uses passive elements to greatly increase gain. It is built along a support boom that is pointed toward the signal, and thus sees no induced signal and does not contribute to the antenna's operation. The end closer to the source is referred to as the front. Near the rear is a single active element, typically a half-wave dipole or folded dipole. Passive elements are arranged in front (directors) and behind (reflectors) the active element along the boom. The Yagi has the inherent quality that it becomes increasingly directional, and thus has higher gain, as the number of elements increases. However, this also makes it increasingly sensitive to changes in frequency; if the signal frequency changes, not only does the active element receive less energy directly, but all of the passive elements adding to that signal also decrease their output as well and their signals no longer reach the active element in-phase.
Does this device improve the operation of the antenna?
A: does not contribute
Problem: Please answer a question about the following article about American Idol:
Caleb Johnson was named the winner of the season, with Jena Irene as the runner-up. Johnson released "As Long as You Love Me" as his coronation single while Irene released "We Are One".
Who came in second on season 13 of American Idol?
A: Jena Irene
Problem: Please answer a question about the following article about Brain:
The first vertebrates appeared over 500 million years ago (Mya), during the Cambrian period, and may have resembled the modern hagfish in form. Sharks appeared about 450 Mya, amphibians about 400 Mya, reptiles about 350 Mya, and mammals about 200 Mya. Each species has an equally long evolutionary history, but the brains of modern hagfishes, lampreys, sharks, amphibians, reptiles, and mammals show a gradient of size and complexity that roughly follows the evolutionary sequence. All of these brains contain the same set of basic anatomical components, but many are rudimentary in the hagfish, whereas in mammals the foremost part (the telencephalon) is greatly elaborated and expanded.
At how many mya did mammals first appear in time?
A: 200 Mya
Problem: Please answer a question about the following article about Umayyad Caliphate:
Around 746, Abu Muslim assumed leadership of the Hashimiyya in Khurasan. In 747, he successfully initiated an open revolt against Umayyad rule, which was carried out under the sign of the black flag. He soon established control of Khurasan, expelling its Umayyad governor, Nasr ibn Sayyar, and dispatched an army westwards. Kufa fell to the Hashimiyya in 749, the last Umayyad stronghold in Iraq, Wasit, was placed under siege, and in November of the same year Abu al-Abbas was recognized as the new caliph in the mosque at Kufa.[citation needed] At this point Marwan mobilized his troops from Harran and advanced toward Iraq. In January 750 the two forces met in the Battle of the Zab, and the Umayyads were defeated. Damascus fell to the Abbasids in April, and in August, Marwan was killed in Egypt.
Who became leader of the Khurasan Hashimiyya in approximately 746?
A:
Abu Muslim