Which of the following is an antibiotic ?

Options

A. Sodium bicarbonate
B. streptomycein
C. alcohol
D. yeast

Answer

### Step-by-Step Solution:

1. **Understand the Definition of Antibiotics**:
- Antibiotics are medicines that help to kill or inhibit the growth of bacteria and other microbes. They are specifically used to treat infections caused by these microorganisms.

2. **Analyze the Options Provided**:
- The question presents four options: sodium bicarbonate, streptomycin, alcohol, and another unspecified option.

3. **Evaluate Each Option**:
- **Sodium Bicarbonate**: This is primarily used as a preservative and does not have antibiotic properties. It helps in increasing the shelf life of food.
- **Streptomycin**: This is an antibiotic that is specifically used to treat tuberculosis, a serious bacterial infection that affects the lungs.
- **Alcohol**: While it has antiseptic properties, it is not classified as an antibiotic. It is produced in anaerobic conditions and is used for disinfection but does not kill bacteria in the same way antibiotics do.

4. **Identify the Correct Answer**:
- Among the options analyzed, **streptomycin** is the only substance that qualifies as an antibiotic.

5. **Conclusion**:
- The correct answer to the question "Which of the following is an antibiotic?" is **streptomycin**.