Final answer:
The Arthurian legends were written and expanded upon by various authors, with Sir Thomas Malory being a significant figure for compiling the stories in 'Le Morte d'Arthur.' Characters like Merlin and King Arthur are subjects of the legend, not its creators.
Step-by-step explanation:
None of the characters listed in the student's question - Merlin, King Arthur, Sir Lancelot, or Morgan le Fay - are directly responsible for the creation of the Arthurian legend. These are characters within the legend itself. The Arthurian legend is a collective work that has been contributed to by many authors over the centuries. However, a key contributor to the mythology as we know it today was the medieval writer Sir Thomas Malory, who penned 'Le Morte d'Arthur' in the 15th century, which compiled and brought together many of the existing stories about King Arthur, the Knights of the Round Table, and the quest for the Holy Grail.
Moreover, poets and writers such as Geoffrey of Monmouth and Alfred, Lord Tennyson later expanded and popularized these legends. Tennyson's work, for instance, includes 'The Lady of Shalott,' which draws from Arthurian elements. So in essence, while the legendary characters played roles in shaping the narrative through their storied actions, they were not the creators of the legend