**Core Concept**
Ureidopenicillins are a class of beta-lactam antibiotics derived from penicillin. They have a ureido side chain attached to the beta-lactam ring, which enhances their stability and potency. Ureidopenicillins are effective against a wide range of Gram-positive and Gram-negative bacteria.

**Why the Correct Answer is Right**
The correct answer is a ureidopenicillin because it has a ureido side chain attached to the beta-lactam ring. This modification increases the drug's resistance to beta-lactamase enzymes, which are produced by some bacteria to break down penicillins. The ureido side chain also enhances the drug's affinity for penicillin-binding proteins (PBPs) on bacterial cell walls, leading to inhibition of cell wall synthesis and ultimately bacterial death.

**Why Each Wrong Option is Incorrect**
* **Option A:** This drug is actually a carboxypenicillin, not a ureidopenicillin. Carboxypenicillins have a carboxyl group attached to the beta-lactam ring, rather than a ureido group.
* **Option B:** This drug is a cephalosporin, not a ureidopenicillin or a penicillin. Cephalosporins have a six-membered beta-lactam ring, rather than the five-membered ring found in penicillins.
* **Option D:** This drug is an aminopenicillin, not a ureidopenicillin. Aminopenicillins have an amino group attached to the beta-lactam ring, rather than a ureido group.

**Clinical Pearl / High-Yield Fact**
Ureidopenicillins are often used to treat infections caused by Pseudomonas aeruginosa, a Gram-negative bacterium that can be resistant to many other antibiotics.

**Correct Answer:** C.