2. Which of the following are the biochemical features of S. typhi? They are: 1. lactose-negative H_(2)S-positive 3. glucose-positive 4. oxidase-positive

The correct answer is:1. lactose-negative2. -positive3. glucose-positiveExplanation:Salmonella typhi (S. typhi) is a Gram-negative bacterium that exhibits the following biochemical features:1. Lactose-negative: S. typhi does not ferment lactose, so it is lactose-negative.2. -positive: S. typhi produces hydrogen sulfide ( ) when grown on certain media, such as Triple Sugar Iron (TSI) agar, making it -positive.3. Glucose-positive: S. typhi can ferment glucose, so it is glucose-positive.The fourth option, oxidase-positive, is incorrect. S. typhi is oxidase-negative, meaning it does not produce the enzyme cytochrome c oxidase.