This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Direct immunofluorescence(DIF) is negative in: 
Select and explain. 
A. Bullous Pemphigoid, B. Cicatricial pemphigoid, C. Epidermolysis Bullosa Dystrophica, D. Pemphigus Folaceous
C: Epidermolysis Bullosa Dystrophica
Answer: C: Epidermolysis Bullosa Dystrophica 
Explanation: All of the above are autoimmune disorders except Epidermolysis Bullosa Dystrophica which is because of defective collagen.7 in dermis and hence DIF is negative.