Read the passage below and choose the correct answer for questions 136-140

As long as 340 BC, the Greek philosopher Aristotle in his book 'On the Heavens', was able to put forward two good statements for believing that the earth was a round sphere rather than a flat plate. First he realised that eclipses of the moon were caused by the earth coming between the sun and the moon. The earth's shadow on the moon was always round, which would be true only if the earth was spherical. If the earth had been a flat disc, the shadow would have been elongated and elliptical, unless the eclipse always occurred at a time when the sun was directly under the centre of the disc. Second, the Greeks knew from their travels that the North star appeared lower in the sky when viewed in the South than it did in the more northerly regions (since the North star lies over the North pole), it appears to be directly above an observer at the North pole, but to someone looking from the equator, it appears to lie just at the horizon, From the difference in the apparent position of the North star in Egypt and Greece, Aristotle estimated the distance around the earth was 400,000 stadia.