**Core Concept**
Cephalosporins are a class of beta-lactam antibiotics that exhibit antibacterial activity by inhibiting cell wall synthesis in susceptible bacteria. Their spectrum of activity varies among different generations, and some cephalosporins exhibit enhanced activity against specific pathogens, including Pseudomonas aeruginosa.

**Why the Correct Answer is Right**
Pseudomonas aeruginosa is a Gram-negative bacterium that is inherently resistant to many antibiotics. However, certain cephalosporins, particularly those in the fourth and fifth generations, have been shown to exhibit good activity against this pathogen. These cephalosporins, such as ceftazidime and cefepime, have a broad spectrum of activity that includes Pseudomonas aeruginosa due to their ability to penetrate the bacterial cell wall and inhibit cell wall synthesis.

**Why Each Wrong Option is Incorrect**
**Option A:** Cephalotin is a first-generation cephalosporin that lacks activity against Pseudomonas aeruginosa, making it an incorrect choice.
**Option B:** Ceftriaxone, a third-generation cephalosporin, has some activity against Pseudomonas aeruginosa, but it is not considered a primary treatment option.
**Option C:** Cefepime, a fourth-generation cephalosporin, is known for its good activity against Pseudomonas aeruginosa, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
When treating Pseudomonas aeruginosa infections, it is essential to use antibiotics that exhibit good activity against this pathogen, such as ceftazidime, cefepime, or tobramycin.

**Correct Answer: A. Cephalotin**