"President Jefferson believed that the future of America lay in the West. Now that so much new land belonged to the United States, he wanted to have it explored. He hoped to find a
waterway across North America to the Pacific Ocean."

Thomas Jefferson was the third president of the United States between 1801 and 1809. He was a politician who fervently defended expansion to the west, relying on the doctrine of Manifest Destiny, which urged the United States to expand towards the Pacific Ocean. Thus, during his government, he took several measures in this direction: the Louisiana Purchase, which doubled the territory of the United States, expanding it westward, and the Lewis and Clark expedition, which consolidated American sovereignty over these territories.

Precisely, the phrase of the question refers precisely to the Lewis and Clark Expedition, which occurred between 1804 and 1806, by means of which President Jefferson entrusted the explorers to find a river route from the East Coast to the Pacific.

your answer is c) experiments with water vapor showed that elements combine in specific proportions.