Answer: I believe It would be C. The Louisiana Purchase.
Explanation: The Louisiana Purchase happend in the 1803 where Louisiana Purchase expands U.S. territory west of the Mississippi River.
At the beginning of both World War I and World War II, the initial policy of the United States was to "remain neutral", since the United States during these times was a very "isolationist" nation.
Carbonic acid's chemical formula is H2CO3. Its decomposition to water (H2O) and carbon dioxide (CO2) is represented by the equation