What were the causes of the Mexican-American War?

I think its B but yeah if it's wrong I'm sorry

answer; slavery should be outlawed in the new country, was part of the initial draft of the declaration of independence, but not part of the final

in february 1787, congress decided that a convention should be convened to revise the articles of confederation, the nation’s first constitution. in may, 55 delegates came to philadelphia, and the constitutional convention began. debates erupted over representation in congress, over slavery, and over the new executive branch. the debates continued through four hot and muggy months. but eventually the delegates reached compromises, and on september 17, they produced the u.s. constitution, replacing the articles with the governing document that has functioned effectively for more than 200 years.