This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Impoant Bacterial Diseases in Children, Subject name: Pediatrics
A 5-year-old unimmunised child presented with sore throat & swelling of neck. On examination of throat, the following was seen. What is the most probable causative organism? 
Select and explain. 
A. Streptococcus pyogenes, B. Mycobacterium tuberculosis, C. Staphylococcus aureus, D. Corynebacterium diphtheriae
D: Corynebacterium diphtheriae
Answer: D: Corynebacterium diphtheriae 
Explanation: A membrane is seen over the tonsil in this child with swelling of neck: suggestive of Diphtheria. Diphtheria typically follows an incubation period of 2-5 days. - Infection is slower in onset with less local discomfo often resembling a typical viral upper respiratory infection (URI) - Localized or coalescing pseudo membrane in diphtheria extends beyond the tonsils, on to the soft palate and is diy grey in colour. It is characterized by the formation of a dense, gray debris layer composed of a mixture of dead cells, fibrin, RBCs, WBCs, and organisms - It is adherent, and its removal leaves a bleeding surface. - Urine may show albumin. - Smear and culture of throat swab will reveal corynebacterium diphtheriae