The answer to you question
D
Answer:
Chester A. Arthur
Explanation:
Chester A. Arthur was the 21st president of the United States.
His time as president began in 1881 and ended in 1885.
The important contribution to navigation made by Eratosthenes in the third-century bc was a reasonably accurate calculation of the circumference of our planet.
Who is Eratosthenes?
Eratosthenes was born in 276 BC and died in 194 BC. He was a well-known poet, mathematician, a researcher in geography, and theorist of music. He was the first to gauge the size of the planet.
The Earth was first measured by Eratosthenes of Cyrene. The precise measurement of Earth's circumference was greatly aided by Eratosthenes' work in the third-century bc.
As a result, the Eratosthenes in the third century bc accurate calculation of the Earth.
Learn more about Eratosthenes, here:
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The truman doctrine offered aid to any country threatened by communism. SO any government that was liable to turn to communism the truman doctrine aided those countries so that those countries might instead turn to democracy.
