This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
All are true regarding diphtheria toxin except 
Select and explain. 
A. Toxins blocks elongation of protein, B. Beta lysogenic strain produces toxin, C. Iron is critical for toxin production, D. Toxic is necessary for local wound infection
D: Toxic is necessary for local wound infection
Answer: D: Toxic is necessary for local wound infection 
Explanation: Virulent strains of diphtheria bacilli produce a very powerful exotoxin. The pathogenic effects of the bacillus are due to the toxin. Almost all strains of gravis and intermedius are toxigenic. The toxin is extremely potent and the lethal dose for a 250 g guinea pig is 0.0001g. The toxin has a special affinity for ceain tissues such as the myocardium, adrenals and nerve endings. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 240