Meriwether lewis and william clark open the american frontier to settlement by

Meriwether Lewis and William Clark helped open the American frontier to settlement by exploring the regions further out west. They mapped these territories and found accessible routes, so that Americans could move further out west and settle the land before the Europeans could claim it. There was also a smaller objective of studying the science and possible economic qualities.

It's most likely choice a, it makes the most sense in my opinion.