At the beginning of the Mexican War in 1846, when "American blood was spilled on American soil," General Zachary Taylor and his troops were ______.
At the beginning of the Mexican War in 1846, when American blood was spilled on American soil, General Zachary Taylor and his troops were north of the Rio Grande River in territory claimed by both Mexico and the United States. Zachary Taylor was the general whom James K. Polk sent to provoke war with Mexico in 1846. The territory between the Nueces River in Texas and the Rio Grande to the south was disputed. It was claimed by both Mexico and the United States. The Mexicans shot at Taylor, who was on the land they claimed. The provocation worked, and the war did not end until 1848. The quote in the question was by Polk, who claimed that the border of Texas was the Rio Grande so that it was American soil.
In 1846, California (A), New Mexico (C), and Utah (E) were not American soil and they were territories gained after the Mexican War in the Treaty of Guadalupe-Hidalgo in 1848.
There was a border dispute between New Mexico and Texas, but Taylor did not negotiate that. Taylor was a general, not an admiral in the Navy, so (D) is not correct.