Nobody of them.
G-d & Gabriel have never passed something written to Mohammed.
Mohammed himself was an analphabet. The Sira of Ibn Ishaq and the Hadith is here very clear.
So somebody else has written the quran.
No one has written it! It is just a collection of Mohammeds,'s preachings. When he died, his brother-in-law (one of them
) Uthman aksed people all over Arabia to bring him pieces of leather or stones with gravations of M.'s preaches or preaches written on paper. Then he let it be re-written, put into a specific order and bound it to a book, called "The Reading" - the quran.
The problem with this was, that he rewarded people bringing him preaches and some things were obviously not M.'s preachings leading to many contradictions in the whole collection.
Just as 3 versions of the story of the Creation of the World...