**Core Concept**
Brucella is a genus of Gram-negative bacteria that primarily affects animals, causing zoonotic infections in humans. Brucellosis, the disease caused by Brucella, is an undulant fever with systemic symptoms, and its transmission is often linked to consumption of contaminated dairy products or direct contact with infected animals.

**Why the Correct Answer is Right**
Brucella is a facultative intracellular pathogen that thrives in aerobic environments but can survive in anaerobic conditions. However, it requires oxygen for its growth and replication. Pasteurization, which involves heat treatment, effectively kills Brucella bacteria. Additionally, Brucella is indeed associated with undulant fever, and its Gram-negative coccobacilli morphology is a distinguishing feature. The bacteria are typically found in animal tissues and can be transmitted to humans through various routes.

**Why Each Wrong Option is Incorrect**
**Option A:** Undulant fever, also known as Malta or Mediterranean fever, is indeed a characteristic of Brucellosis. Brucella infections often present with systemic symptoms, including fever, malaise, and weight loss.
**Option B:** Brucella is correctly identified as a Gram-negative coccobacilli. This morphology helps distinguish it from other pathogens.
**Option C:** Pasteurization is effective in killing Brucella bacteria, making this statement true. Pasteurization involves subjecting liquids to high temperatures for a short period, which is sufficient to inactivate Brucella.

**Clinical Pearl / High-Yield Fact**
It is crucial to recognize the zoonotic potential of Brucella, which can be transmitted to humans through contact with infected animals or contaminated dairy products. This highlights the importance of proper animal handling, vaccination, and pasteurization to prevent Brucellosis.

**✓ Correct Answer: D. It is a strict anaerobe**