**Core Concept**
The clearance of a substance is a measure of its renal excretion rate, representing the volume of plasma from which the substance is completely removed per unit time. It is an important parameter in assessing renal function.

**Why the Correct Answer is Right**
To calculate clearance, we use the formula: Clearance (Cl) = (Urine concentration x Urine flow) / Plasma concentration. Given values are: Urine concentration = 100 mg%, Urine flow = 2 ml/min, and Plasma concentration = 10 mg%. Substituting these values in the formula, we get: Cl = (100 mg% x 2 ml/min) / 10 mg% = 20 ml/min.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** Not applicable, as the correct formula and calculation are used.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
Remember, clearance is an important indicator of renal function and is used to assess the capacity of the kidneys to remove waste products from the blood.

**Correct Answer:** B. 20 ml/min