Final answer:
Based on the provided excerpts, there is no clear indication of Eliza's thoughts about Polly's death, as the excerpts reference different literary contexts and characters named Eliza without a cohesive narrative about Polly.
Step-by-step explanation:
The texts presented seem to reference different characters named Eliza and instances of death, but the question specifically about what Eliza thinks could have caused Polly's death is not directly addressed in the excerpts provided. It appears there is some potential confusion as the characters and contexts in the excerpts do not align with a situation where Eliza is contemplating Polly's death. Therefore, a definitive answer cannot be provided based on the given information. However, analyzing the context of the excerpts given, it seems they are from different literary works and do not form a cohesive narrative regarding Polly's death and Eliza's thoughts about it.