**Core Concept**
The underlying principle being tested is the concept of **reciprocal antagonism** or **functional antagonism** in pharmacology, where two different chemicals acting on different receptors produce opposite effects on the same cell.

**Why the Correct Answer is Right**
Although the correct answer options are missing, in general, when two chemicals act on two different receptors and their response is opposite to each other on the same cell, it is an example of **functional antagonism**. This occurs when two agents have opposite effects on the same physiological function, often through different receptor mechanisms.

**Why Each Wrong Option is Incorrect**
**Option A:** This would be incorrect because it does not describe the interaction of two different chemicals acting on different receptors with opposite effects.
**Option B:** Similarly, this option would not accurately represent the concept of two chemicals with opposite effects on the same cell through different receptors.
**Option C:** This option would also be incorrect as it does not align with the definition of functional antagonism.
**Option D:** Assuming this is not the correct answer, it would be incorrect because it does not describe the scenario provided.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **functional antagonism** is different from **pharmacological antagonism**, where one drug directly blocks the action of another by binding to the same receptor.

**Correct Answer:** D. Functional antagonism.