Identify the correct statement.

The correct option is: "Blood pressure in pulmonary circulation is less than that of the systemic circulation".

To understand why this statement is correct, let us analyze the physiological differences between the pulmonary and systemic circulatory systems:
1. Systemic Circulation: This pathway carries oxygenated blood from the left ventricle of the heart to the rest of the body's organs and tissues, and returns deoxygenated blood back to the right atrium. Because it has to pump blood throughout the entire body (often against gravity), the left ventricle must contract with significant force. Consequently, the systemic circulation operates under much higher pressure (typically around 120/80 mmHg in humans) to ensure blood reaches all peripheral tissues.
2. Pulmonary Circulation: This pathway carries deoxygenated blood from the right ventricle to the lungs for oxygenation and returns oxygenated blood to the left atrium. Since the lungs are located in close physical proximity to the heart, the right ventricle does not need to pump blood very far. As a result, the pulmonary vascular resistance is much lower, and the blood pressure in the pulmonary circulation is significantly lower (typically around 25/10 mmHg) to prevent fluid from leaking into the lung alveoli (which would cause pulmonary edema).

Thus, the blood pressure in the pulmonary circulation is indeed much less than that of the systemic circulation.

Let us briefly review why the other options are incorrect:
- "Double circulation is characteristic of all vertebrates": This is incorrect because fishes, which are vertebrates, have a single circulatory system where blood passes through the heart only once during a complete circuit.
- "Volume of blood in pulmonary circulation is more than the volume of blood in systemic circulation at any instant": This is incorrect. The systemic circulation is a much larger network and holds a significantly larger portion of the total blood volume at any given moment compared to the smaller pulmonary network.
- "a double aortic arch is seen in birds and mammals": This is incorrect. Birds possess a right systemic arch, while mammals possess a left systemic arch; neither group has a double aortic arch in their adult forms (unlike some reptiles).