Which of the Following Was Not One of the Causes

Which of the following was not one of the causes of increasingly tense relations between the Mexican government and the American residents in Texas after 1830?

A) The instability of Mexican politics
B) Attempts by the Mexican government to prohibit importation of slaves
C) The failure of the Mexican government to pay $2 million in debts owed to American citizens.
D) The bitter memories that American residents held of the Alamo and the Goliad massacre.
E) The desire of the Mexican government to sell Texas to the United States.