## **Core Concept**
The core concept being tested here is the treatment of plague, a serious bacterial infection caused by *Yersinia pestis*. The management of plague involves the use of specific antibiotics that are effective against this pathogen.

## **Why the Correct Answer is Right**
Streptomycin is an aminoglycoside antibiotic that is effective against *Yersinia pestis*, the causative organism of plague. It works by inhibiting bacterial protein synthesis, which ultimately leads to the death of the bacteria. Streptomycin is considered a drug of choice for treating plague, particularly for bubonic and pneumonic plague, which are the most common forms of the disease.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although doxycycline is used as an alternative for prophylaxis and treatment of plague, especially in cases where streptomycin is not available, it is not the first-line treatment.
- **Option B:** This option is incorrect because ciprofloxacin, a fluoroquinolone, can be used for plague but is not considered the drug of choice.
- **Option D:** This option is incorrect because gentamicin, another aminoglycoside like streptomycin, can be effective but is not the preferred choice for treating plague.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that streptomycin is the first-line treatment for plague, but doxycycline and ciprofloxacin can be used as alternatives under certain circumstances. Early treatment is critical in reducing mortality from plague.

## **Correct Answer:** . Streptomycin