**Core Concept**
Selective β2 antagonists are a class of medications that block the action of β2-adrenergic receptors, which are predominantly found in the smooth muscle of the bronchi, uterus, and blood vessels. This blockade leads to relaxation of smooth muscle and dilation of blood vessels, resulting in bronchodilation and vasodilation.

**Why the Correct Answer is Right**
The correct answer is a selective β2 antagonist because it preferentially binds to β2-adrenergic receptors, thereby inhibiting the action of epinephrine and norepinephrine on these receptors. This selectivity allows for the desired therapeutic effects on the respiratory and cardiovascular systems without causing significant side effects on the cardiovascular system. The β2-adrenergic receptors are coupled to Gs-proteins, which activate adenylyl cyclase and increase cyclic AMP levels, leading to smooth muscle relaxation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a selective β2 antagonist, as it has significant effects on α1-adrenergic receptors, leading to vasoconstriction and increased blood pressure.
**Option B:** This option is not a selective β2 antagonist, as it has a non-selective blockade of both β1 and β2-adrenergic receptors, leading to unwanted effects on the cardiovascular system.
**Option C:** This option is not a selective β2 antagonist, as it has a partial agonist activity on β2-adrenergic receptors, leading to a mixed agonist-antagonist effect.

**Clinical Pearl / High-Yield Fact**
Selective β2 antagonists are commonly used in the treatment of asthma and chronic obstructive pulmonary disease (COPD) to prevent bronchospasm and improve lung function. They are also used to treat certain cardiovascular conditions, such as supraventricular tachycardia and hypertension.

**Correct Answer:** C. **Tiotropium**