**Core Concept**
The resting membrane potential (RMP) of a neuron is the difference in electrical charge between the interior and exterior of the cell when it is at rest, not transmitting or receiving signals. This potential is generated by the movement of ions across the cell membrane, primarily sodium (Na+) and potassium (K+).

**Why the Correct Answer is Right**
The correct answer, **-70mV**, is the average RMP of a typical mammalian neuron. This value is determined by the balance between the inward movement of positively charged sodium ions and the outward movement of positively charged potassium ions across the cell membrane. The RMP is maintained by the selective permeability of the cell membrane to these ions, which is regulated by various ion channels and pumps. The RMP is essential for the proper functioning of neurons, as it allows them to generate action potentials when stimulated.

**Why Each Wrong Option is Incorrect**
**Option A:** -9mV is too positive and does not accurately reflect the RMP of a typical neuron.
**Option B:** -50mV is still too positive and does not account for the significant contribution of potassium ions to the RMP.
**Option D:** -100mV is too negative and would be more characteristic of a depolarized or excited neuron.

**Clinical Pearl / High-Yield Fact**
The RMP is a crucial factor in determining the excitability of neurons, and changes in the RMP can lead to various neurological disorders, such as epilepsy or hypokalemia. It's essential to remember that the RMP is a dynamic parameter that can be influenced by various factors, including ion channel function, membrane potential, and external stimuli.

**✓ Correct Answer: C. -70mV**