Final answer:
The writer should delete the underlined sentence because it does not provide a transition from the previous paragraph and fails to support the main argument.
Step-by-step explanation:
The writer should delete the underlined sentence because it does not provide a transition from the previous paragraph. Transitions are important for guiding readers and helping them follow the flow of ideas. By removing the sentence, the writer can improve the coherence of the passage and ensure that the main argument is effectively supported.