The correct option is D. An immediate effect was Andrew Johnson’s ascension to the presidency; a long-term effect was conflict between Johnson and Radical Republicans.
After the assassination of U.S. President Abraham Lincoln, on April 14, 1865, Vice President Andrew Johnson became President. Although at first, he appeared to be a Radical, he broke with them, mainly because of the Civil Rights Act of 1866 and four Reconstruction Acts, involving him in a bitter struggle with Radical Republicans.
In such political struggle, the Radical Republicans, who had full control of Congress, were able to override 15 of the 21 bills passed by Congress, which Johnson had vetoed.