**Core Concept**
Meningiomas are a type of tumor that arises from the meninges, the protective membranes surrounding the brain and spinal cord. These tumors are typically slow-growing and can be either benign or malignant. Understanding the origin and attachment of meningiomas is crucial for accurate diagnosis and treatment.

**Why the Correct Answer is Right**
The correct answer, **Option C: They are attached to pia mater**, is incorrect. Meningiomas typically arise from the arachnoid cap cells, which are part of the arachnoid mater, but not from the pia mater. The arachnoid mater is one of the three layers of the meninges, and the pia mater is the innermost layer that directly adheres to the surface of the brain and spinal cord. Meningiomas can be attached to the dura mater, the outermost layer of the meninges, or to the falx cerebri, the falx cerebelli, or other structures, but not specifically to the pia mater.

**Why Each Wrong Option is Incorrect**
**Option A:** Meningiomas are predominantly benign tumors of adults. This statement is true, as meningiomas are typically slow-growing and benign, with the majority occurring in adults.
**Option B:** They arise from the meningothelial cell of the arachnoid. This statement is also true, as meningiomas arise from the meningothelial cells of the arachnoid mater.
**Option D:** Occur in association with eighth nerve schwannomas. This statement is true, as meningiomas can occur in association with other tumors, including eighth nerve schwannomas, which are tumors of the Schwann cells that cover the eighth cranial nerve.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that meningiomas can be associated with neurofibromatosis type 2 (NF2), a genetic disorder characterized by the growth of tumors in the nervous system, including meningiomas and schwannomas. This association can help in the diagnosis and management of patients with NF2.

**✓ Correct Answer: C. They are attached to pia mater**