The pulmonary circuit:

The correct answer is choice A. True.

Blood flow through a capillary is controlled by a precapillary sphincter, which opens or closes due to the requirements of the cells supplied by the capillary.

This allows blood to bypass the capillaries when they are not needed and to increase blood flow when they are needed.

Choice B. False is wrong because it contradicts the true statement in choice A. A precapillary sphincter is a ring of smooth muscle that surrounds the entrance of a capillary and regulates blood flow into it.

It is influenced by local factors such as oxygen, carbon dioxide, pH, and temperature.

The pulmonary circuit sends oxygen-poor blood to the lungs, where it is oxygenated and returned to the heart.
This is distinguished from the systemic circuit, which sends oxygen-rich blood to the tissues and returns oxygen-poor blood to the heart.
Choice A is wrong because it confuses the pulmonary circuit with the systemic circuit. The pulmonary circuit does not send blood to the tissues but to the lungs.
Choice B is wrong because it only describes part of the pulmonary circuit.
The pulmonary circuit sends oxygen-poor blood to the heart, but only after it has been oxygenated in the lungs.
Choice C is wrong because it confuses the pulmonary circuit with the systemic circuit. The pulmonary circuit does not bring blood from the tissues but from the heart.