**Core Concept**
Dobutamine is a synthetic catecholamine with inotropic, chronotropic, and vasodilatory properties. It acts on specific adrenergic receptors to increase cardiac contractility and heart rate.

**Why the Correct Answer is Right**
Dobutamine primarily acts on **β1-adrenergic receptors** in the heart, which increases the contractility of the heart muscle (inotropic effect). This action is mediated through the activation of the Gs protein, leading to an increase in cAMP levels and subsequent activation of protein kinase A (PKA). PKA phosphorylates and activates the L-type calcium channels, increasing calcium influx and cardiac contractility.

**Why Each Wrong Option is Incorrect**
* **Option A:** α-adrenergic receptors are primarily involved in vasoconstriction, which is not the primary action of dobutamine.
* **Option B:** β2-adrenergic receptors are involved in bronchodilation and vasodilation, particularly in the peripheral vasculature, but not in the primary action of dobutamine.
* **Option D:** This option is blank and cannot be evaluated.

**Clinical Pearl / High-Yield Fact**
Dobutamine is often used in critical care settings to support patients with cardiogenic shock or heart failure, particularly when there is a need for increased cardiac contractility. However, it can also lead to tachycardia and hypertension, which may require careful monitoring and management.

**Correct Answer:** C. β1-adrenergic receptors.