The Mexican-American War was in the period 1846-1848. The main causes of the Mexican-American War were mainfest destiny (Americans believed that thye have the right to expand westward and conquer territory despite the rights of the indigenous people already living on that land), westward expansion, economics, and slavery
The first alternative is correct (A).
A war is a terroir scenario, where the soldiers go through very difficult times. Many lose friends, see the suffering of people, children, anyway. That way, no matter how psychologically strong a soldier is, his emotional state is shaken.
The Vietnam War itself caused many traumas, as it was a very violent war with many deaths and mutilations. In this way, soldiers who have returned alive have gone through many psychological dramas, alcohol vices, drugs, to the point of needing rehabilitation programs.
<span>Assuming that this is referring to the same list of options that was posted before with this question, <span>the correct response would be the "railroad," since rail travel allowed for people and supplies to move to the west at an unprecedented pace. </span></span>
