## **Core Concept**
The question tests knowledge of antibiotics, specifically antipseudomonal penicillins. Pseudomonas aeruginosa is a notorious pathogen that requires targeted antimicrobial therapy. Antipseudomonal penicillins are a class of β-lactam antibiotics effective against this organism.

## **Why the Correct Answer is Right**
The correct answer, **C. Piperacillin**, is a broad-spectrum, antipseudomonal penicillin. It belongs to the ureidopenicillin subclass, which is known for its efficacy against Pseudomonas aeruginosa. Piperacillin's mechanism of action involves inhibiting cell wall synthesis in bacteria, ultimately leading to cell lysis and death. It is often combined with tazobactam, a β-lactamase inhibitor, to broaden its spectrum and prevent degradation by β-lactamases.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Ticarcillin is an antipseudomonal penicillin but is less commonly used compared to piperacillin. It is also often combined with clavulanate to extend its spectrum.
* **Option B:** This option seems to be missing a specific antibiotic name but based on common antipseudomonal penicillins, if it were to represent another antibiotic like mezlocillin or azlocillin, these are less frequently referenced or have limited use against Pseudomonas compared to piperacillin.
* **Option D:** Without a specific antibiotic listed, it's hard to directly refute, but generally, other penicillins like ampicillin or amoxicillin are not effective against Pseudomonas aeruginosa.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **piperacillin-tazobactam** is a commonly used combination for empirical treatment in severe infections, especially in ICU settings, due to its broad-spectrum activity, including against Pseudomonas. This combination is often considered a first-line treatment for various infections where Pseudomonas could be a potential pathogen.

## **Correct Answer:** C. Piperacillin.