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: Skin
A 16-year-old boy presented with asymptomatic, multiple, erythematous, annular lesions with a collarette of scales at the periphery of the lesions present on the trunk. The most likely diagnosis is: 
Select and explain. 
A. Pityriasis versicolor, B. Pityriasis alba, C. Pirityasis rosea, D. Pityriasis rubra pilaris
C: Pirityasis rosea
Answer: C: Pirityasis rosea 
Explanation: Lesions predominantly localized to the trunk and their erythematous nature with other features of pityriasis lead to diagnosis of pityriasis rosea. Ref: Anthony Du Vivier, Phillip H. McKee, Chapter 6, "Pityriasis Rosea and Pityriasis Rubra Pilaris", In the book, "Atlas of Clinical Dermatology", Elsivier Publication, 2002, 3rd Edition, Spain, Page 87