Which option best explains Tennyson's decision to include Lancelot in his poem "Lady of Shalott"?

The Lady of Shalott is a magical being who lives alone on an island upstream from King Arthur's Camelot. Her business is to look at the world outside her castle window in a mirror, and to weave what she sees into a tapestry. She is forbidden by the magic to look at the outside world directly. The farmers who live near her island hear her singing and know who she is, but never see her.