**Core Concept:**
Plague is a severe bacterial infection caused by the bacterium Yersinia pestis. It is transmitted to humans through the bite of an infected flea, or through direct contact with infected animals or bodily fluids. Antibiotics are the primary treatment for plague. The drug of choice depends on the stage and severity of the infection.

**Why the Correct Answer is Right:**
The correct answer is **D.** Doxycycline, a tetracycline antibiotic, is the drug of choice for plague treatment. It works by inhibiting bacterial protein synthesis and has a broad spectrum of activity against gram-positive and gram-negative bacteria, including Yersinia pestis.

**Why Each Wrong Option is Incorrect:**

A. Streptomycin (Option A) is an aminoglycoside antibiotic and has activity against gram-negative bacteria, including Yersinia pestis. However, it has poor oral bioavailability, limiting its usage in treating plague.

B. Gentamicin (Option B) is another aminoglycoside antibiotic with activity against gram-negative bacteria. Similar to Streptomycin, its poor oral bioavailability makes it an unsuitable choice for treating plague.

C. Fluoroquinolones (Option C) are a class of antibiotics with activity against gram-negative bacteria, including Yersinia pestis. However, their use in treating plague is limited due to potential side effects and resistance development.

**Clinical Pearl:**
Plague can be a life-threatening disease if left untreated. Early initiation of appropriate antibiotics like doxycycline is crucial for successful treatment and prevention of complications.

**Correct Answer:** Doxycycline (Option D) is the drug of choice for plague treatment due to its good oral bioavailability, broad-spectrum activity against Yersinia pestis, and fewer side effects compared to other antibiotic options.