Question

what was a cause of the mexican war?
the annexation of oregon
the belief in manifest destiny
the imbalance of free states and slave states
the refusal of the u.s. to pay mexico for acquiring texas

Explanation:

• "the annexation of Oregon" was related to the Oregon boundary dispute, not the Mexican War.
• "the belief in manifest destiny" was a key cause as it drove the U.S. to expand westward, including into Mexican - claimed territory. The U.S. believed it was their destiny to spread across the continent, which led to tensions with Mexico over land like Texas and the Southwest.
• "the imbalance of free states and slave states" was a cause of later conflicts like the Civil War, not the Mexican War.
• The U.S. did not refuse to pay Mexico for acquiring Texas in a way that caused the Mexican War; in fact, the U.S. annexed Texas (which Mexico still considered its territory) and the dispute over the Texas - Mexico border (and the U.S. desire for more Mexican territory) along with manifest destiny - driven expansion led to the war.

Answer:

B. the belief in manifest destiny