This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
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Question: Passage: AA gunnery was a difficult business. The problem was of successfully aiming a shell to burst close to its target's future position, with various factors affecting the shells' predicted trajectory. This was called deflection gun-laying, 'off-set' angles for range and elevation were set on the gunsight and updated as their target moved. In this method when the sights were on the target, the barrel was pointed at the target's future position. Range and height of the target determined fuse length. The difficulties increased as aircraft performance improved. Question: What was the problem with AA gunnery?

Answer: successfully aiming a shell to burst close to its target's future position


Question: Passage: The Cathedral of Brasília in the capital of the Federative Republic of Brazil, is an expression of the architect Oscar Niemeyer. This concrete-framed hyperboloid structure, seems with its glass roof reaching up, open, to the heavens. On 31 May 1970, the Cathedral’s structure was finished, and only the 70 m (229.66 ft) diameter of the circular area were visible. Niemeyer's project of Cathedral of Brasília is based in the hyperboloid of revolution which sections are asymmetric. The hyperboloid structure itself is a result of 16 identical assembled concrete columns. These columns, having hyperbolic section and weighing 90 t, represent two hands moving upwards to heaven. The Cathedral was dedicated on 31 May 1970. Question: When was the Cathedral of Brasília dedicated?

Answer: 31 May 1970


Question: Passage: Tuvaluans are well known for their seafaring skills, with the Tuvalu Maritime Training Institute on Amatuku motu (island), Funafuti, providing training to approximately 120 marine cadets each year so that they have the skills necessary for employment as seafarers on merchant shipping. The Tuvalu Overseas Seamen's Union (TOSU) is the only registered trade union in Tuvalu. It represents workers on foreign ships. The Asian Development Bank (ADB) estimates that 800 Tuvaluan men are trained, certified and active as seafarers. The ADB estimates that, at any one time, about 15% of the adult male population works abroad as seafarers. Job opportunities also exist as observers on tuna boats where the role is to monitor compliance with the boat's tuna fishing licence. Question: What is the only trade union on Tuvalu?

Answer:
Tuvalu Overseas Seamen's Union