The most accurate answer regarding how Native Americans were affected by westward expansion is:
3) They faced the loss of a major food source due to buffalo hunting.
Westward expansion led to significant changes in the environment and the economy, including extensive buffalo hunting, which decimated buffalo populations and severely impacted the livelihoods of many Native American tribes that relied on buffalo for food, clothing, and tools. While there were instances of treaties and military service, the realities of westward expansion often resulted in displacement, conflict, and resource loss for Native Americans.