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
Which of the following are bacterial infection of skin? 
Select and explain. 
A. Pyoderma gangrenosum, B. Piedra, C. Impetigo contagiosa, D. Impetigo herpetiformis
C: Impetigo contagiosa
Answer: C: Impetigo contagiosa 
Explanation: C i.e. Imetigo contagiosaPiedra is a fungal infection of hair. Pyoderma gangrenosum is a rare, serious ulcerative disorder that is often d/t serious underlying systemic disease eg ulcerative colitis, chron's disease, rheumatoid ahritis or myeloma etc. Impetigo herpetiformis is the synonym of generalized pustular psoriasis of pregnancy.