to enable the character to share thoughts with the reader directly
Answer: The right answer is the A) To enable the character to share thoughts with the reader directly.
Explanation: Just to elaborate a little on the answer, it can be added that option B must be discarded, since it is an overstatement. Even though writing in first-person does reveal the characters’ thoughts and feelings, it can't reveal them all. Precisely because the author is writing in first-person he/she can decide what to reveal and what to conceal. In addition, it is possible to argue that option C is also misleading, since by writing in first-person there is no other perspective but that of the character, and that perspective is all the reader has at his/her disposal. However, writing in first-person enables the character to share thoughts with the reader directly, without filters. The reader gets in the character's head and behind the character's eyes, and witnesses the succession of events that unfold from that character's, and only that character's, perspective. If the author is writing in present tense, then that character's thoughts and experiences will be revealed even more vividly.