Answer: d) She adapted to new circumstances by convincing herself that she agreed with her husband’s views.
"Apt" means astute, or clever. In this case, Douglass uses the word in order to convey a certain adaptability and flexibility of mind that Mrs. Auld possessed. Even though she wanted to educate her slaves, her husband soon convinced her that this was a bad choice. Because she was "apt," she adapted by trying to convince herself that her husband was right, and she was successful.