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
A 30 year old male came with pruritic papule over flexor aspect of right forearm which is purple in colour.There is also pterygium of nails. Diagnosis? 
Select and explain. 
A. Alopecia areata, B. Psoriasis, C. Lichen planus, D. Pityriasis rosea
C: Lichen planus
Answer: C: Lichen planus 
Explanation: Purple,pruritic lesion over flexor aspect & pterygium of nail is suggestive of Lichen planus.