## **Core Concept**
The question tests knowledge of cephalosporins, a class of β-lactam antibiotics, and their antimicrobial activity, specifically against *Pseudomonas aeruginosa*, a Gram-negative bacterium known for causing infections, particularly in immunocompromised individuals and those with cystic fibrosis.

## **Why the Correct Answer is Right**
Cephalosporins are categorized into generations based on their antimicrobial spectrum and activity. The fourth-generation cephalosporin, **Cefepime**, has a broad spectrum of activity that includes *Pseudomonas aeruginosa*. This is due to its stability against β-lactamase degradation and its ability to penetrate bacterial cells effectively. **Cefepime** is used in severe infections, including pneumonia, urinary tract infections, and febrile neutropenia.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While first-generation cephalosporins like **Cefazolin** have good activity against Gram-positive bacteria, they lack significant activity against *Pseudomonas aeruginosa*.
- **Option B:** Second-generation cephalosporins, such as **Cefuroxime**, have increased activity against Gram-negative bacteria but do not effectively cover *Pseudomonas aeruginosa*.
- **Option D:** Third-generation cephalosporins, like **Ceftriaxone**, have broad-spectrum activity but generally do not have reliable activity against *Pseudomonas aeruginosa*, with some exceptions like **Ceftazidime**, but **Ceftriaxone** is not known for anti-pseudomonal activity.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that when *Pseudomonas aeruginosa* is suspected or confirmed, antibiotics with anti-pseudomonal activity should be used. **Cefepime** and **Ceftazidime** are cephalosporins with notable anti-pseudomonal activity. Always consider local resistance patterns when choosing an antibiotic.

## **Correct Answer:** C. Cefepime.