Why did J.R.R. Tolkien write The Hobbit and other stories of Middle-earth?

AHe wanted to design a complex imaginary world in which he could set a large number of tales.
BHe wanted to convince readers that Middle-earth was real and that the events of his stories truly happened.
CHe wanted to record a factual history of the British Isles.
DHe wanted to add to legends that already existed about Middle-earth.

Verified Answer :

Nobody really knows why exactly J.R.R. Tolkien wrote his middle earth lore.  Many believe or have learned that Tolkien spoke of an ancient document, documenting all of the events and likewise that had really happened in the Middle Earth time.  There is honestly no correct or incorrect answer, as nobody truly knows why he wrote it except for the dead man himself.

a. He wanted to design a complex imaginary world in which he could set a large number of tales. would be the best option due to his sons description in the Silmarillion.