**Core Concept**
Partial agonists are a class of drugs that exhibit a mixed agonist-antagonist property, where they can both stimulate and block the receptor to varying degrees. The intrinsic activity of a drug refers to its ability to produce a maximal response at a receptor, with a value of 1 representing a full agonist, 0 representing an antagonist, and a value between 0 and 1 representing a partial agonist.

**Why the Correct Answer is Right**
For a partial agonist, the intrinsic activity value should be between 0 and 1, as it can only produce a submaximal response at the receptor. This is because partial agonists have a limited ability to activate the receptor, resulting in a reduced maximal effect compared to full agonists. The intrinsic activity value of a partial agonist is often used to quantify its efficacy and potency.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because an intrinsic activity value of 0 would indicate an antagonist, which does not produce any response at the receptor.
**Option B:** Incorrect because an intrinsic activity value of 1 would indicate a full agonist, which produces a maximal response at the receptor.
**Option C:** Incorrect because an intrinsic activity value of 2 would be an invalid value, as intrinsic activity is a measure of the drug's efficacy and cannot exceed 1.

**Clinical Pearl / High-Yield Fact**
When evaluating the efficacy of a partial agonist, it's essential to consider its intrinsic activity value, as it can provide valuable insights into its therapeutic potential and potential side effects.

**Correct Answer:** C.