In all other options, you can become a citizen in USA. If you are born inside the territory belongs to the USA or born to US parents in anywhere in the world or through Naturalization.
However, buying Lands and owning property within USA will not make you a Citizen of the USA.
By selling land given to them to build the railroad
Explanation:
The government gave the railroad companies large amounts of land to sell both so that the railroad companies earn some money and so they can speed up the settling of the frontier.
