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.

[Q]: Passage: Mach argued that, in effect, the water experiment in an otherwise empty universe would remain flat. But if another object were introduced into this universe, perhaps a distant star, there would now be something relative to which the bucket could be seen as rotating. The water inside the bucket could possibly have a slight curve. To account for the curve that we observe, an increase in the number of objects in the universe also increases the curvature in the water. Mach argued that the momentum of an object, whether angular or linear, exists as a result of the sum of the effects of other objects in the universe (Mach's Principle). Question: Mach argued that the momentum of an object exists as a result of the sum of the effects of what?
[A]: effects of other objects in the universe


[Q]: Passage: Gibraltar opened its first comprehensive school in 1972. Between the ages of 12 and 16 two comprehensive schools cater for girls and boys separately. Students may also continue into the sixth form to complete their A-levels. Question: When was the first comprehensive school opened in Gibraltar?
[A]: 1972


[Q]: Passage: The government planned to voluntarily evacuate four million people—mostly women and children—from urban areas, including 1.4 million from London. It expected about 90% of evacuees to stay in private homes, and conducted an extensive survey to determine available space. Detailed preparations for transporting them were developed. A trial blackout was held on 10 August 1939, and when Germany invaded Poland on 1 September a blackout began at sunset. Lights would not be allowed after dark for almost six years, and the blackout became by far the most unpopular aspect of the war for civilians, more than rationing.:51,106 The relocation of the government and the civil service was also planned, but would only have occurred if necessary so as not to damage civilian morale.:33 Question: The government planned to evacuate 1.4 million from which city?
[A]:
London