The correct answer is C) She is allowed to show the same lights as a sailing vessel. This is correct because the International Regulations for Preventing Collisions at Sea (COLREGS) state that a vessel under oars is considered a sailing vessel for the purposes of the navigation lights required. Therefore, a vessel under oars is allowed to show the same lights as a sailing vessel, which includes a stern light, sidelights, and a masthead light or all-round white light. The other options are incorrect because a vessel under oars is not required to show a black cone day shape (A), a flashing all-round white light (B), or a stern light alone (D). The regulations allow a vessel under oars to display the same lights as a sailing vessel.