This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
On blood agar target appearance of Cl. perfringens is due to which toxin - 
Select and explain. 
A. Lecithinase, B. Phospholipase, C. a-toxin, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is 'd' i.e., All of the above * Two important characteristic feature of Cl. perfringens are1) Target hemolysis (double zone hemolysis) on blood agar. It is a narrow zone of complete hemolysis by theta toxin which is surrounded by a wider incomplete hemolysis by alpha-toxin.2) Naegler's reaction detects alpha toxin (phospholipase or lecithinase C). When Cl. perfringens is grown on a medium with the antitoxin spread on one half of the plate, colonies on the other half without the antitoxin will be surrounded by a zone of opacity. There will be no opacity around the colonies on the half of the plate with the antitoxin, due to the specific neutralisation of the alpha-toxin.* Alpha toxin is phospholipase (lecithinase-C).