To determine what caused Brown to fall (Part A), we would need to analyze the content of the poem in question. However, since I don't have access to the specific poem or its content, I can't provide a definitive answer.
For Part B, the lines that support the answer would similarly depend on the actual text of the poem.
If you have the text of the poem or additional context, please share it, and I can help analyze it to answer your questions!