PLEASE HELP! All of the following were causes of the 1846 Mexican American war except

a) disagreement between the United States and Mexico over location of the southern United States border

b) unpaid debts owed the United States that the Mexican govt. had stopped making payments on

c) fighting in the Rio Grande Valley between the military forces of Zachary Taylor and Gen Mejia

d) the U. S. effort to overthrow the Mexican govt. in California led by John Fremont​