The figurative language used is Personification. This is Personification because darkness was given human qualities. The word 'darkness' symbolizes depression or emotional instability. 'Slumber summons me to play' means that sleep is the only option to escape from reality and forgetting about responsibilities. The reader feels the emotion from this because it makes the reader imagine what it's like.
The right answer is the last one: The natural imagery is developed throughout to indicate that nature continues long after humans do. The theme of this poem by the renowned American poet Henry Wadsworth Longfellow (1807-1882) is about the unavoidable passage of time for humans and the repetitive essence and continuity of nature, which, unlike the former (who, as the traveler in the poem, one day stop going back to the shore) is endlessly rising, falling, and returning, like the tide. The elements from nature that are mentioned in the poem - the tide, the sea, the waves - are beautifully personified by Longfellow, making the comparison between the temporality of human life and the permanency of nature even more poignant.
