Which of the following is a symptom indicating a decrease in pulmonary blood flow?

A symptom indicating a decrease in pulmonary blood flow is often related to conditions that restrict blood flow to the lungs, which can lead to significant clinical manifestations. The complete closure of the tricuspid valve is relevant in this context because if this valve were fully closed, it would prevent blood from flowing from the right atrium to the right ventricle and subsequently to the pulmonary artery. This blockage would drastically reduce the blood flow to the lungs, causing a decrease in oxygenation and potentially leading to cyanosis or other symptoms associated with impaired pulmonary circulation.

In contrast, the other options typically reflect conditions that do not directly indicate decreased pulmonary blood flow. Bounding pulses, for example, often indicate increased blood flow or decreased vascular resistance, typically seen in conditions like patent ductus arteriosus. A harsh murmur might indicate turbulence in the blood flow, which can occur in various heart defects but doesn’t specifically signify decreased pulmonary blood flow. A fast heart rate can occur in response to many different cardiac and systemic conditions but is also not specific to decreased pulmonary blood flow. Thus, the closure of the tricuspid valve stands out as a critical indicator of reduced pulmonary circulation in this situation.