I believe the answer may be D. In taking action, one must not worry about success or failure.
The Americans simply wanted the land for themselves, they pushed the natives further out towards California, used them as slaves before Africans. Give me a time frame so I can answer the problem better
Writers help the urban poor by writing about their lives and their difficulties in populated cities and poor hygiene conditions. Which brought the attention of the upper class and the government to reform and improve the lives of the working class.
Too much stock speculation and overproduction in industry and agriculture.
The most important event was obviously the American Civil War from 1861-1865. This led to the 14th Amendment which defined a citizen as "any person born or naturalized in the US." The 13th Amendment abolished slavery, and the 15th Amendment prohibits denying the right to vote to someone because of their race.
Other key events include the Louisiana Purchase, the Texas Revolution, The Spanish-American War, the War of 1812, the purchase of Alaska, the Mexican Cession, the Indian Wars, and the California Gold Rush.
Like I said, the right to vote was extended to all male citizens by the 15th Amendment. Women were not given the right to vote until the 19th Amendment was passed in 1920.