## **Core Concept**
The question tests knowledge of the antimicrobial spectrum of various cephalosporins, specifically their activity against *Pseudomonas aeruginosa*. Cephalosporins are a class of β-lactam antibiotics with a broad range of activity, but not all are effective against *Pseudomonas* species.

## **Why the Correct Answer is Right**
The correct answer, **Ceftazidime**, is a third-generation cephalosporin known for its broad-spectrum activity, including efficacy against *Pseudomonas aeruginosa*. This is due to its stability against β-lactamase degradation and its ability to bind to penicillin-binding proteins (PBPs) in *Pseudomonas*, ultimately inhibiting cell wall synthesis. Other cephalosporins may have varying degrees of activity but are not reliably effective against *Pseudomonas*.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Cefazolin (or Cefazoline in some regions) is a first-generation cephalosporin with good activity against Gram-positive bacteria but limited activity against Gram-negative bacteria, including no reliable activity against *Pseudomonas aeruginosa*.
- **Option B:** Ceftriaxone is a third-generation cephalosporin with broad-spectrum activity but lacks reliable activity against *Pseudomonas aeruginosa*, unlike ceftazidime.
- **Option D:** Cefepime is a fourth-generation cephalosporin with a broad spectrum of activity, including against *Pseudomonas aeruginosa*. However, given that **Ceftazidime** is listed as the correct answer and also has anti-pseudomonal activity, the focus remains on **Ceftazidime**.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that when *Pseudomonas aeruginosa* infection is suspected or confirmed, antibiotics with anti-pseudomonal activity, such as ceftazidime, cefepime, ciprofloxacin, or piperacillin-tazobactam, should be considered. *Pseudomonas* infections are particularly concerning in immunocompromised patients and those with cystic fibrosis.

## **Correct Answer: C. Ceftazidime**