Under the terms of the Gulf of Tonkin Resolution, President Johnson a. was given the authority to take strictly limited measures to preserve the independence of South Vietnam b. was forced to reduce the American troop commitment to South Vietnam c. was given the authority to provide an open-ended commitment to the preservation of South Vietnamese independence d. was allowed to increase American support for Ngo Dinh Diem and his circle of advisors e. was required to withdraw American troops from South Vietnam after sixty days without a congressional declaration of war