Final answer:
The approach Mary likely used to gain access to an all-white school would involve court orders or government intervention following civil rights rulings, not the options given in the multiple-choice question.
Step-by-step explanation:
The question seems to have been inspired by the struggles faced by African Americans during the civil rights movement, particularly regarding school integration. In one historical instance, Mary McLeod Bethune and other activists fought for the rights of African Americans to attend schools with white students. Legal challenges and direct appeals to government officials were methods used to gain admittance, as in the case of James Meredith at the University of Mississippi.
Given the provided context, Mary did not forge a letter from the president to attend classes at an all-white school. Instead, these types of admittances were typically gained through court orders, direct government intervention, or the actions of civil rights advocates leveraging rulings such as Brown v. Board of Education to enforce desegregation. The question possibly references the broader struggles for civil rights and access to education, rather than a specific historical figure named Mary.