Which of the following was partly an effect of the Mexican-American War?
a. the start of a prolonged depression
b. a dramatic weakening of the federal government
c. the United States becoming a transcontinental nation
d. Polks rising unpopularity among American expansionists
e. the taking of all of Mexico by the United States

The correct answer is letter "C": the United States becoming a transcontinental nation.

Explanation:

After Texas was declared independent from Mexico in 1836, issues arose since the U.S. did not want to annex the freed territory due to northern interests. Mexico became hostile in defining the frontiers after the independence of Texas at the point of threatening the U.S. to go on war if its demand was not fulfilled.  

With an attack on American Soldiers by April 1846 in Texas, the war begun. Americans military power revealed superior to Mexicans winning the war in favor of U.S. President James K. Polk (1795-1849) who believed the U.S. had to spread across the continent.

The effect of the war was California, Utah, Nevada, and Arizona being annexed to the U.S. territory.

you can put this in your 11 sentence summary

" most of the money would be invested in innovation, economic convergence."