Final answer:
Streptomycin is the correct answer for the question 'Which of the following is an antibiotic?' as it is an aminoglycoside antibiotic effective against gram-negative bacteria and inhibits protein synthesis.
Step-by-step explanation:
The question 'Which of the following is an antibiotic?' refers to a substance used to treat bacterial infections by inhibiting the growth or destroying bacteria. Among the options given, Streptomycin is the correct answer. Streptomycin is categorized as an aminoglycoside antibiotic and is effective against gram-negative bacteria. It works by binding to the 30S subunit of bacterial ribosomes, altering their shape and causing a misreading of messenger RNA, which ultimately inhibits protein synthesis.
By contrast, Sodium bicarbonate is a chemical compound used for a variety of purposes, including baking and as an antacid, but it is not an antibiotic. Alcohol is a disinfectant that can kill bacteria on surfaces but is not used to treat bacterial infections within the body. Finally, Yeast is a type of fungus used in baking and brewing; it is not an antibiotic and does not have antimicrobial properties against bacterial infections.