## Core Concept
Selective β3-blockers are a class of medications that specifically target β3-adrenergic receptors, which are primarily found in adipose tissue and play a role in lipolysis. These blockers are less likely to affect the heart and lungs, which are primarily influenced by β1 and β2 receptors, respectively.

## Why the Correct Answer is Right
β3-blockers are unique in their selectivity for β3-adrenergic receptors. They are used in research and potentially in clinical settings for their effects on metabolism and possibly on heart failure and diabetes. The correct answer, , is not a selective β3-blocker, implying it has a different receptor selectivity profile compared to the others listed.

## Why Each Wrong Option is Incorrect
* **Option A:** is considered a selective β3-blocker, making it incorrect as an exception.
* **Option B:** is also a selective β3-blocker, which is why it's incorrect as an exception.
* **Option C:** is another selective β3-blocker, making it incorrect as an exception.

## Clinical Pearl / High-Yield Fact
A key point to remember is that β3-blockers have potential therapeutic applications in obesity and type 2 diabetes due to their role in inhibiting lipolysis and improving insulin sensitivity. However, their clinical use is still under research.

## Correct Answer: .