Which "act of Mexico herself," referred to by President Polk in this passage, was the cause of

war between the United States and Mexico?
(1 point)
Mexico’s refusal to discuss the U.S. offer to buy California and New Mexico
Mexico’s massacre of the Alamo defenders
Mexican soldiers’ attack on General Zachary Taylor’s forces in a disputed border area
Mexico’s refusal to honor the U.S. annexation of Texas

And your answer is? We'll be glad to check it.

The "act of Mexico herself" referred to by President Polk in this passage, which was the cause of the war between the United States and Mexico, is Mexico's refusal to honor the U.S. annexation of Texas. Mexico refused to recognize Texas as part of the United States after Texas declared independence from Mexico in 1836 and subsequently joined the United States as a state in 1845. This refusal by Mexico to accept the annexation of Texas by the United States was a major point of contention and one of the main reasons that led to the outbreak of the Mexican-American War.