B. strengthen the ability of native populations to secure independence
One advantages of having more than one political party is you have different perspectives and ideas on how to solve problems. One disadvantage is the different parties will have a hard time agreeing and solving problems because they will both think their right.
According the the Homestead Act of 1862, the only two valid answers are A. Settlers had to promise to avoid contact with American Indian tribal lands and D. Settlers had to improve the land (e.g., by buying a house) to keep it.
