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: Unknown
A child scratches his hand with a pen. A red wheal appears which persists for 30 minutes. What would be the diagnosis? 
Select and explain. 
A. Atopy, B. Contact urticarial, C. Pressure urticarial, D. Dermographism
D: Dermographism
Answer: D: Dermographism 
Explanation: (Refer: Fitzpatrick's Dermatology in General Medicine, 8th edition, pg no: 414-420)
Variant forms of physical urticaria