Before we can choose the correct answer, we must first understand what an inference is. According to the dictionary, an inference is a piece of knowledge, or opinion, that you form after having gathered the information regarding a specific topic or subject. It can also be a conclusion that results from considering data or information on a topic. The result may not be directly stated, in fact, it never is, but through the facts that you have, you can draw such conclusions without a fault. In this case, Douglass, the character, infers that freedom is already at hand for him, even if physically this has not yet happen. As if freedom were not necessarily tied to legalities or the physical world. Within him, the character already feels freedom. This is why the correct answer is choice B: I now resolved that, however long I might remain a slave in form, the day had passed forever when I could be a slave in fact.
