Final answer:
Congress was pushed to create the Military Reconstruction Act due to the Southern states' refusal to ratify the Fourteenth Amendment, fearing its defeat, which signaled the need for a more stringent approach to Reconstruction.
Step-by-step explanation:
The main reason Congress created the Military Reconstruction Act was, in essence, due to the fear that the Fourteenth Amendment might be defeated (option b). The stubborn resistance of the Southern states to ratify the Fourteenth Amendment signaled to Congress that the South remained 'unreconstructed' and adverse to the significant changes being sought, particularly regarding African American citizenship and civil rights.
Republicans, with a strong majority following the elections of 1866, responded with the Reconstruction Acts of 1867, dividing the South into military districts and setting strict requirements for readmission to the Union. The Acts were a direct challenge to President Johnson's lenient approaches, including his previous vetoes such as against the bill to reauthorize the Freedmen's Bureau, and his insistence on the more lenient Ten Percent Plan advocated by Lincoln.