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
Most common organism causing T. capitis is – 
Select and explain. 
A. Trichophyton tonsurans, B. Microsporum, C. Epidermophyton, D. Candida albicans
B: Microsporum
Answer: B: Microsporum 
Explanation: "Ringworm of the scalp occurs in children exclusively and is mainly due to M. canis".
Following statement of Harrison creats some confusion here :-
"The predominent organism is T tonsurans".

Therefore, I had to do extensive search on this question and I collected following information :
Most common organism causing Ectothrix is M. canis, whereas most common organism causing Endothrix is T tonsurans. Ectothrix is the most common type of T. capitis, therefore M. canis would be the most common cause of T. capitis.