**Core Concept**
The equilibrium potential of a specific ion is the membrane potential at which the electrical and chemical gradients for that ion are equal, resulting in no net movement of the ion across the cell membrane. In the case of calcium (Ca2+), the equilibrium potential is primarily determined by the concentration gradient of calcium ions across the cell membrane.

**Why the Correct Answer is Right**
The equilibrium potential for calcium (E_Ca) can be calculated using the Nernst equation: E_Ca = (RT/F) * ln([Ca2+]_out / [Ca2+]_in), where R is the gas constant, T is the temperature in Kelvin, F is the Faraday constant, and [Ca2+]_out and [Ca2+]_in are the concentrations of calcium ions outside and inside the cell, respectively. Since the concentration of calcium ions is typically much higher outside the cell than inside, the equilibrium potential for calcium is typically negative, around -70 to -90 mV.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so we'll skip it.
* **Option B:** This option is also not provided, so we'll skip it.
* **Option C:** This option is not provided, so we'll skip it.
* **Option D:** This option is not provided, so we'll skip it.

**Clinical Pearl / High-Yield Fact**
The equilibrium potential for calcium is an important concept in understanding the electrical activity of neurons and muscle cells. A key point to remember is that the equilibrium potential for calcium is typically negative, which means that calcium ions tend to flow into the cell down their concentration gradient, contributing to the depolarization of the cell membrane.

**Correct Answer:** Not provided, but the correct answer is typically a numerical value, such as -80 mV.