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
Diffuse form of hyperpigmentation is seen in- 
Select and explain. 
A. Vitamin B12, deficiency, B. Ectopic ACTH secretion, C. Whipple's disease, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: All the given options can cause diffuse hyperpigmentation (for detail read the causes of hyperpigmentation from the text of this chaptor).