**Core Concept**
The mastoid antrum is a critical structure in the temporal bone that plays a crucial role in the drainage of the middle ear. It is an air-filled cavity that connects the middle ear cavity to the mastoid air cells.

**Why the Correct Answer is Right**
The mastoid antrum is located in the petrous part of the temporal bone, specifically in the posterior aspect of the middle ear cavity. It is a pear-shaped cavity that is connected to the epitympanic recess by the aditus ad antrum. The mastoid antrum is lined by mucous membrane and contains the promontory, which is a bony projection that houses the basal turn of the cochlea. The antrum is also connected to the mastoid air cells, which are a network of air-filled cavities that extend into the mastoid process.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the mastoid antrum is not located in the squamous part of the temporal bone, which is a thicker, flat portion of the bone that forms the sides and rear of the skull.
* **Option B:** This option is incorrect because the mastoid antrum is not located in the tympanic part of the temporal bone, which is a smaller, thinner portion of the bone that forms the outer wall of the middle ear cavity.
* **Option C:** This option is incorrect because the mastoid antrum is not located in the occipital bone, which is a separate bone that forms the back and base of the skull.

**Clinical Pearl / High-Yield Fact**
The mastoid antrum is an important landmark in otosclerosis, a condition characterized by abnormal bone growth in the middle ear that can cause hearing loss. The antrum is often involved in the disease process, and its location is critical for surgical procedures aimed at relieving the condition.

**Correct Answer:** C. Petrous part of temporal bone.