Answer: a book about pigs
Step-by-step explanation:
The source that would be the most unreliable source for a research on pigs would be a book about pigs.
A local pig farmer would be a reliable source as he is involved with the animals daily and therefore knows what they eat, how they mate, how they give birth and other things relating to them.
Also, a veterinarian and a friend with a pet pig would also give a reliable source of the research as they also have first hand experience with them.
The book on pigs is and unreliable source