This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'C.diphtheriae can be biochemically differentiated from C.ulcerans by \nSelect and explain. \nA. Catalase test, B. Urease test, C. Oxidase test, D. Nitrate Reduction', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Among the Corynebacterium species, all are catalase positive. All are resistant to tellurite. All Corynebacterium species are oxidase negative. C. ulcerans is differentiated from C. diphtheriae by its negative nitrate reduction and positive gelatin liquefaction. 3 species produce diphtheria toxin: C. diphtheriae, C. ulcerans, and C. pseudotuberculosis. C. ulcerans- closely related to C.diphtheriae; causes bovine mastitis; Can cause acute pharyngitis in humans; C. ulcerans has been repoed to cause a few cases of diphtheria', 'role': 'assistant'}]