The correct answer is D. It helped explorers determine their position at sea.
Step-by-step explanation:
The astrolabe is an instrument mainly used for navigators and astronomers as with this it is possible to determine one's position in terms of altitude or the location of stars and other celestial bodies. Indeed during the Age of Discovery, in which Europeans aimed at finding new lands and routes, this instrument was used by explorers to determine the position were they were at sea, mainly by using the horizon and the distance of this in reference to the sun and stars which help sailors to know whether they were at the north or the south of the Equator line. Therefore, the astrolabe helped Europeans explorers mainly because by using this they could determine their position at sea and follow a specific route according to the maps available back then.