What was one contribution made by eratosthenes in ancient greece

a. he wrote a geometry textbook that was used for nearly 2,000 years

b. he calculated the value of the infinite number known as pi

c. he computed the circumference of planet earth

d. he developed military tactics that still apply today

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

(C)-He computed the circumference of planet Earth.

Explanation:

I just know :)

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.

uncle sam would be tossing and turning in his grave : *)