Final answer:
A. true. The Lewis and Clark Expedition proved that the continent was wider than what was popularly believed.
Step-by-step explanation:
The statement that "The Lewis and Clark Expedition proved that the continent was wider than what was popularly believed" is true.
The Lewis and Clark Expedition was led by Meriwether Lewis and William Clark from 1804 to 1806. Their purpose was to explore the new western lands and discover potential trade routes. Although they did not find the long-sought Northwest Passage, their expedition added greatly to the knowledge of the territory west of the Mississippi River.
The expedition brought back a wealth of information on the geography, Native American tribes, and the flora and fauna of the areas they explored. It also helped solidify the United States' claim to the vast territory. The accurate mapping of the territory showed that the continent was wider than popularly believed.