**Core Concept**
The question requires the identification of an antibiotic that can be used as an alternative in patients who are sensitive to penicillin. This involves understanding the pharmacological properties of antibiotics, particularly those in the beta-lactam class, which includes penicillins.

**Why the Correct Answer is Right**
Cephalosporins, specifically the first-generation cephalosporins, are often used as alternatives to penicillin in patients who are sensitive to penicillin. This is because they have a similar mechanism of action, which involves inhibiting cell wall synthesis in bacteria, but they have a different chemical structure that allows them to bypass the penicillin-binding proteins (PBPs) that are responsible for the allergic reaction in sensitive individuals.

The correct answer is a first-generation cephalosporin, which is effective against a range of Gram-positive and Gram-negative bacteria. First-generation cephalosporins, such as cefazolin, are commonly used in surgical prophylaxis and for the treatment of skin and soft tissue infections.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a particular antibiotic class or mechanism of action that would make it suitable for use in penicillin-sensitive patients.
**Option B:** This option is incorrect because it is a macrolide antibiotic, which has a different mechanism of action and is not typically used as a substitute for penicillin.
**Option C:** This option is incorrect because it is a fluoroquinolone antibiotic, which has a different mechanism of action and is not typically used as a substitute for penicillin.

**Clinical Pearl / High-Yield Fact**
When choosing an antibiotic for a patient who is sensitive to penicillin, it is essential to consider the mechanism of action and the chemical structure of the antibiotic, as well as the patient's specific infection and any relevant allergies.

**Correct Answer:** C. Cefazolin.