The correct answer is D. Mexican war.
Mexican war was started over the border dispute.
Mexican war was a conflict which was armed and it was between United Mexican States and United States of America.
This war followed the annexation of Americans for the Republic of Texas Independence. The Mexican government was forced into remnant by treaty of Guadalupe Hidalgo to end the war and to end mexican cession.
In Mexico it became a state of ruin and degradation because there was domestic turmoil, territories, national prestige, and losses of life.