Which legislation passed by congress authorized the use of force in vietnam? . . a. the marshall plan. . b. the national defense education act. . c. the gulf of tonkin resolution. . d. the war powers act.

The legislation that was passed by Congress and authorized the use of force in Vietnam was the Gulf of Tonkin Resolution. The correct option among all the options that are given in the question is the third option or option "C". This resolution was passed by the United States Congress on 7th of August in the year 1964.