What evidence indicates that president lincoln began writing his speech prior tothe train ride to gettysburg?

What evidence indicates that President Lincoln began writing his speech prior to the train ride to Gettysburg? A.Earlier drafts of the speech have been found on Executive Mansion stationary. B.President Lincoln had a habit of practicing his speeches for other people so there are witnesses who heard it prior to the ceremony. C.President Lincoln had to give his speech writers enough time to write the speech and get his approval. D.President Lincoln mentions in a diary entry that he began writing the speech the day he received his invitation to the ceremony.

Ibeileve it will be c. : )