Final answer:
The answer to the fill-in-the-blank question is 'settlers and mountain men', as they were the ones who assisted future travelers in navigating the challenges of the Oregon Trail during the westward expansion.
Step-by-step explanation:
The Oregon land and climate continued to attract settlers and mountain men, who helped lead future travelers through mountain passes and up rivers. The correct answer is b. settlers and mountain men.
During the westward expansion, settlers were drawn by the promise of land and opportunity along paths such as the Oregon Trail. Mountain men, skilled in wilderness survival and knowledgeable about the terrain, often acted as guides for these settlers, assisting them in navigating through the challenging environments they faced.
Waves of American settlers and immigrants moved west, not only drawn by the allure of land but also by the ideal of Manifest Destiny. This concept embodied the belief that Americans were destined to expand westward, conquer, inhabit, and thrive in these new territories.