**Core Concept**
The ventricles of the brain are part of the cerebral ventricular system, which is a complex network of fluid-filled spaces that produce and circulate cerebrospinal fluid (CSF). The ventricles are lined by a specialized type of epithelial tissue that plays a crucial role in CSF production and circulation.

**Why the Correct Answer is Right**
The correct answer is ependyma, a type of epithelial tissue that lines the ventricles and central canal of the spinal cord. Ependymal cells produce and circulate CSF, which helps to cushion the brain and spinal cord, remove waste products, and regulate intracranial pressure. The ependyma is a single layer of cells that forms a continuous lining around the ventricles and central canal.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a type of tissue that lines the ventricles. While the meninges do cover the brain and spinal cord, they are not the primary lining of the ventricles.
**Option B:** This option is incorrect because the choroid plexus is a specialized structure that produces CSF in the ventricles, but it is not the type of tissue that lines the ventricles.
**Option C:** This option is incorrect because the pia mater is one of the layers of the meninges that covers the brain and spinal cord, but it is not the primary lining of the ventricles.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the ependyma is a specialized type of epithelial tissue that plays a critical role in CSF production and circulation. Damage to the ependyma can lead to hydrocephalus, a condition characterized by an accumulation of CSF in the ventricles.

**Correct Answer: D. Ependyma**