The best example of a factor that led to the start of the Mexican-American War was the US voted to annex Texas. Thus, option 1st is correct.
The factor led American to settle in Northeast region is that there were large cities. Thus, option 2nd is correct.
What was the Mexican-American war?
Mexican American war was the first armed battle which took place in 1846 and lasted for two years. It put President James K. Polk's expansionist administration against a politically fractured and militarily unprepared Mexico.
The US's decision to annex Texas is the best illustration of a cause that contributed to the outbreak of the Mexican-American War. Because of the presence of huge cities, Americans moved to the Northeast region.
Therefore, it can be concluded that option 1st is correct for the first part of the question and option 2nd is correct for the second part of the question.
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