This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Dental
[{'content': 'Most common metal causing contact dermatitis \nSelect and explain. \nA. Zinc, B. Gold, C. Cobalt, D. Nickel', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Nickel allergy is one of the most common causes of contact allergic dermatitis. The most common sites for nickel dermatitis are the earlobes (from earrings), the wrists (from a watch strap) and the lower abdomen (from a jeans stud); the affected areas become intensely itchy and may become red and blistered (acute dermatitis) or dry, thickened and pigmented (chronic dermatitis). Ref Harrison 20th edition pg 1234', 'role': 'assistant'}]