Option 1: accessed -> means to gain entry or obtain; doesn't fit the context of giving up power.
Option 2: adopted -> means to take up or accept; not used with "throne" in this manner.
Option 3: abdicated -> means to voluntarily renounce or give up a position of power, especially a throne.
Option 4: abided -> means to accept or tolerate; grammatically and contextually incorrect here.
Hence, Option 3: abdicated -> "Abdicate the throne" is the correct phrase meaning to voluntarily give up royal power. The word "voluntarily" in the sentence is a key indicator that the king is renouncing his position by choice, which is exactly what abdication means. -> correct