Final answer:
The subject of the question is the history of the Kings of Britain. The correct option for this question is Geoffrey of Monmouth.
Step-by-step explanation:
The subject of the question is English history, specifically the history of the Kings of Britain from 1136-38. The student claims to have based his history on a book in Welsh tongue, but no such book has ever been found. It is believed that he drew on earlier Latin chronicles and fabricated the bulk of his history from Celtic oral tradition, his knowledge of Roman history and literature, and his imagination.
The correct option for this question is Option 1: Geoffrey of Monmouth. Geoffrey of Monmouth is known for his work 'Historia Regum Britanniae' (History of the Kings of Britain), which is believed to be the source of the fabricated history mentioned.