**Core Concept**
Third-generation cephalosporins are a class of beta-lactam antibiotics with broad-spectrum activity against Gram-negative bacteria. They have improved stability against beta-lactamases and are effective against a wide range of pathogens, including those resistant to earlier cephalosporins.

**Why the Correct Answer is Right**
The correct answer is a third-generation cephalosporin due to its mechanism of action, which involves inhibiting bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs). This class of cephalosporins is characterized by their resistance to beta-lactamases and their ability to penetrate into Gram-negative bacteria. Ceftriaxone is a classic example of a third-generation cephalosporin with a long half-life and excellent tissue penetration.

**Why Each Wrong Option is Incorrect**
**Option A:** Cefazolin is a first-generation cephalosporin, which means it has limited activity against Gram-negative bacteria and is more susceptible to beta-lactamases.

**Option B:** Cefepime is a fourth-generation cephalosporin, characterized by its increased stability against beta-lactamases and its ability to penetrate into Gram-negative bacteria. It is often used to treat infections caused by resistant organisms.

**Option C:** Cefotaxime is a third-generation cephalosporin with a broad spectrum of activity against Gram-negative bacteria. It is often used to treat infections such as meningitis and sepsis.

**Clinical Pearl / High-Yield Fact**
When choosing a cephalosporin, remember that the generation number indicates the antibiotic's spectrum of activity and resistance pattern. First-generation cephalosporins are generally effective against Gram-positive bacteria, while third- and fourth-generation cephalosporins have broader activity against Gram-negative bacteria.

**Correct Answer:** D. Cefazolin is the correct answer as it is a first-generation cephalosporin.