Final answer:
The lines that best support the theme of loss and unrealized potential in the poem 'Burning a Book' are, "So I’ve burned books. And there are many / I haven’t even written, and nobody has."
Step-by-step explanation:
The lines from the poem Burning a Book that best support the answer to Part A are likely lines that discuss the theme of loss and the potential of unwritten books, which could contribute to the death of ideas or knowledge. If Part A pertains to the concept of what is lost when books are burned, both literally and metaphorically, then the most relevant lines would be option D: "So I’ve burned books. And there are many / I haven’t even written, and nobody has." (Lines 18-19). This line explicitly addresses the concept of burning books—symbolizing destruction—and also points to the loss of potential knowledge that was never realized or documented, thereby supporting the thematic understanding of the poem.