Born in Cyrene around the year 276 BC, Eratosthenes was an Ancient Greek mathematician and thinker, he even was the leader for some time of the famous Library of Alexandria. He is attributed to have invented geography.
In one of Eratosthenes' most famous experiments, he compared the altitudes of the sun in the sky, in two different locations, one in a northern land and the other one in the south. With these two altitudes, he was able to mathematically calculate with an impressive presition the circumference of the Earth, for this, and other important achievements, some historians state he was way ahead of his time.
So the correct answer is C.) He computed the circumference of planet earth
