Final answer:
Option A is the best paraphrase for lines 43–49, indicating that rules from past studies were used to program networks, which did not yield grid cell behaviors.
Step-by-step explanation:
The best paraphrase of lines 43–49 of the poem seems to be option A, which suggests that the networks were indeed programmed with certain rules based on earlier studies, but despite this programming, they did not demonstrate grid cell behaviors. This interpretation aligns with similar themes in scientific exploration where neural networks, or biological tissues, do not always exhibit expected behaviors despite being influenced by historical data or hypotheses, as discussed in the related texts. Understanding neurons and their connection to behavior remains a complex challenge, akin to interpreting a poem's structure and form for its intended function.