**Core Concept**
Brucellosis is a zoonotic infection caused by Brucella bacteria, which primarily affects animals but can be transmitted to humans through various routes. The transmission of Brucella involves the ingestion of contaminated food, direct contact with infected animals, and inhalation of aerosols.

**Why the Correct Answer is Right**
The primary mode of transmission of Brucella is through direct contact with infected animals or their products, such as unpasteurized milk, cheese, and meat. This is because Brucella bacteria are highly infectious and can be easily transmitted through mucous membranes and skin cuts. The bacteria can also be transmitted through inhalation of aerosols generated from infected animals, such as sheep and goats. However, the transmission through ticks is not a primary mode of Brucella transmission.

**Why Each Wrong Option is Incorrect**
* **Option A:** Direct contact with infected animals is a primary mode of Brucella transmission, making this option incorrect.
* **Option B:** Ingestion of contaminated food, such as unpasteurized milk and cheese, is a common mode of Brucella transmission, making this option incorrect.
* **Option C:** Inhalation of aerosols generated from infected animals is a recognized mode of Brucella transmission, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
It is essential to note that Brucella transmission can occur through various routes, and healthcare workers should take necessary precautions when handling infected animals or their products.

**Correct Answer: D.**