Which of the Following Is Not Among the Reasons That

Which of the following is not among the reasons that Mexican immigrants were sometimes slow to become American citizens?

A) Most lived very close to Mexico and remained identified with that country.
B) Many returned frequently to Mexico to visit home and family there.
C) Almost all Mexican immigrants remained migrant farm laborers unable to settle down in cities.
D) Some Mexican immigrants entered the United States illegally.
E) The Mexican government actively discouraged Mexicans from taking U.S. citizenship.