Ans 3

1 is incorrect because contour lines were used in the 16^th century and the Ordnance Survey wasn't set up until 1791. 2 is incorrect because before the 16^th century contour lines weren't used. 4 is incorrect because they were first used on a map of France and there is no mention of a military purpose. 3 is correct because the speaker says: The first time land contours were used was on a map of France, ... .

Scripts

Map-making has a long and fascinating history - both before Ptolemy produced the first great map of the world and after, up to the beautiful simplicity of the London Underground map and the precisely-detailed Ordnance Survey maps, which cover almost every inch of the United Kingdom. Ancient map-makers used to draw in hills, valleys and rivers to give an idea of the topography, the shape of the land. It wasn't until the late 16^th century that contour lines were used - that is, lines that linked points of the land at the same height - but this was to show the relative depths and shallows of a river. The first time land contours were used was on a map of France, which took about forty years to complete, and was finished in 1783. The Ordnance Survey was set up in 1791 and their maps, as the name suggests, were originally made for military purposes, and the first one to be produced was of the county of Kent at a ratio of one inch to one mile.