The correct answer is "Adding more details about the struggle Rainsford experiences as he swims to the shore".
This excerpt is focusing on a certain episode which occurs to the character of Rainsford. The circumstances of the accident are explained pretty well, but the desperation brought to him is not being conveyed properly. The struggle is mentioned but it's not felt. After explaining all that went wrong, would be best to add details regarding how hard it actually was for Rainsford to solve this situation and how bad he felt. The resolution is given too abruptly in the essay for us to really understand the true dimensions of the incident as it is lacking in detail.
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