Answer: B. The increasing U.S. desire to annex Mexican territories in New Mexico and California
Step-by-step explanation:
The issue that played the largest role in motivating the events Charles Sumner criticizes in "Wrongful Declaration of War Against Mexico" was the increasing U.S. desire to annex Mexican territories in New Mexico and California.
The declaration of war on Mexico by the United States was not justified because the United States only wanted to expand. President Polk didn't respect the boundaries of Mexico.