The most important professional opportunity open to educated African-American women in the early years of the twentieth century was

education

Explanation:

The contribution of the African American women in the upliftment of their society is well known but what remains a grey area is that their contribution towards the whole American society. Their contribution to schools, colleges, civil rights movement was evident in the twentieth century. The success of the civil rights movement provides major opportunities for the African American population and women embraced the role of educators conveniently.