If you are working on a research project in which you must present a short documentary film about the history of your family, The source that would be considered most credible for this project is option B.
Hand-written letters from your great-great grandmother about her immigration.
Those letters will provide too much significant and useful information, data and description pertaining to the history of your family, Every source that comes from any member of the family, especially ancestor will add reliable, credible and accurate proves to what you are going to present in your documentary.
