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
Most common metal causing contact dermatitis 
Select and explain. 
A. Zinc, B. Gold, C. Cobalt, D. Nickel
D: Nickel
Answer: D: Nickel 
Explanation: 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