"Answer" im pretty sure its either C or A, but most likely C.. sorry if you get it incorrect. :(
the answer is (A) the announcement of the Athenian defeat at the battle of the Marathon
Explanation:
After the American attack on Guánica during the Spanish-American War, Spain surrender Puerto Rico (along with the Philippines and Guam). They were then given over to the United States under the Treaty of Paris signed December 10, 1898
B) Truman Doctrine.
I hope this answer is right.
D) continued into the 2010s
