**Core Concept**
Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator that works by increasing the levels of cyclic guanosine monophosphate (cGMP) in the vascular smooth muscle cells of the lungs. This leads to relaxation of pulmonary vascular tone and a decrease in pulmonary vascular resistance.

**Why the Correct Answer is Right**
Inhaled nitric oxide selectively targets the pulmonary vasculature without affecting systemic vasculature. This is due to its ability to diffuse across the alveolar-capillary membrane and bind to soluble guanylyl cyclase in the pulmonary vascular endothelium, leading to increased production of cGMP. The increased levels of cGMP then activate protein kinase G, which causes smooth muscle relaxation and vasodilation. This selective action makes iNO an effective treatment for conditions such as persistent pulmonary hypertension of the newborn (PPHN) and acute respiratory distress syndrome (ARDS).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because iNO does not have significant effects on cardiac function or systemic blood pressure.
**Option B:** This option is incorrect because iNO does not have a significant impact on airway resistance or bronchodilation.
**Option C:** This option is incorrect because iNO is not a bronchodilator and does not have significant effects on airway smooth muscle.

**Clinical Pearl / High-Yield Fact**
Inhaled nitric oxide is a selective pulmonary vasodilator that can be used to improve oxygenation in patients with acute respiratory distress syndrome (ARDS) or persistent pulmonary hypertension of the newborn (PPHN). It is an important treatment option in the management of these conditions.

**Correct Answer: A.**