Rilke writes about a swan, but the swan could symbolize man. Option C is correct.
Rilke’s poem illustrates the clumsiness of swans as they walk. Besides, Rilke compares it to when the swan “lets himself down/ into the water”, and is suddenly shifted into the embodiment of grace. Even though swans lumber on lands “as if in ropes” and are extremely “awkward”, on the water, a swan is one of the most graceful sights.
Thus, Rilke compares MAN with the clumsy swan in life (stumbling along as if in the dark) and that in death (“which is letting go/ of the ground we stand on and cling to every day” ) Man may be akin to the swan on water.