The answer is:
B. In Williams's poem, a farmer is the only witness to Icarus's fall, while Auden mentions both a ploughman and a ship.
Both poems, Williams's "Landscape with the Fall of Icarus" and Auden's "Musée des Beaux Arts," mention the ploughman or farmer, but only Auden's work makes reference to a ship. Nevertheless, in both poems, none of the potential witnesses is able to acknowledge the misfortunate moment Icarus falls in to the sea because all of them are engaged in their everyday activities.