What was the central point of conflict between the United States and Mexico immediately after the U.S. annexed Texas?

A disagreement over trade tariffs on American goods

A dispute over which river marked the official border

A conflict about the rights of American settlers in California

An argument over Mexico's refusal to sell New Mexico

What action did President James K. Polk take to enforce the U.S. claim to the land between the Nueces River and the Rio Grande?

He ordered troops into the disputed area.

He offered to purchase the territory from Mexico.

He asked Great Britain to mediate the disagreement.

He sent diplomats to negotiate a new treaty.

The capture of Mexico City by General Winfield Scott's forces.

The refusal of Mexican officials to meet with an American representative sent to buy territory.

An attack by Mexican forces on a U.S. army patrol near the Rio Grande.

A rebellion of American settlers in California known as the Bear Flag Revolt.

Mexico had failed to govern its northern territories properly.

It was America's manifest destiny to control the entire continent.

Mexico had invaded U.S. land and attacked American soldiers.

Mexico refused to sell California and New Mexico to the U.S.