## **Core Concept**
The question tests knowledge of neuroanatomy, specifically the structure of the meninges surrounding the brain and spinal cord. Leptomeninges are a critical component of these protective layers. The meninges are composed of three layers: the dura mater, arachnoid mater, and pia mater.

## **Why the Correct Answer is Right**
The correct answer, , indicates that the leptomeninges are formed by the arachnoid mater and pia mater. These two layers are collectively known as the leptomeninges because they are thinner and more delicate compared to the dura mater. The arachnoid mater and pia mater are closely associated with the brain and spinal cord, playing crucial roles in protecting these structures and facilitating the circulation of cerebrospinal fluid (CSF).

## **Why Each Wrong Option is Incorrect**
* **Option A:** - This option is incorrect because the dura mater is the outermost, thickest layer of the meninges and is not considered part of the leptomeninges.
* **Option B:** - This option is incorrect because it only mentions one layer, the pia mater, and omits the arachnoid mater, which together form the leptomeninges.
* **Option D:** - This option is incorrect because it likely refers to an incorrect or incomplete combination of meningeal layers, not accurately representing the composition of the leptomeninges.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that infections of the leptomeninges, such as bacterial or viral meningitis, can be life-threatening and require prompt diagnosis and treatment. The leptomeningeal layers are critical in the spread of infection within the central nervous system.

## **Correct Answer:** . Arachnoid mater and Pia mater