What decision by President Polk led to the Mexican-American War

Question

A. Polk signed the Compromise of 1850, a compromise where the U.S. gave Texas $10 million.
B. During Polk’s presidency, Taylor’s forces beat a larger Mexican army at Buena Vista.
C. Polk sent General Zachary Taylor to Texas, and General Taylor settled west of the Nueces River, which was disputed territory in West Texas.
D.Polk sent an envoy to Mexico to try to work out a peace agreement after the U.S. annexed Texas.

Answer 1

C. Polk sent General Zachary Taylor to Texas, and General Taylor settled west of the Nueces River, which was disputed territory in West Texas.