Question

question: in a/an ____ system, the heart pumps blood in one direction around the body. this is found mostly in animals with gills. answer options: select one of four single - loop circulation double - loop circulation closed circulatory open circulatory

Explanation:

To solve this, we analyze the options:

• Double - loop circulation: Involves two circuits (e.g., in mammals and birds), not for gilled animals with one - way blood flow as described.
• Closed circulatory: Blood is confined in vessels, but this doesn't specify the loop type. Many closed circulatory systems can be double - loop.
• Open circulatory: Blood is not always in vessels and doesn't have a single - direction loop typical of gilled animals.
• Single - loop circulation: In this system, blood is pumped in one direction around the body. It is common in animals with gills (like most fish), where the heart pumps blood to the gills, then to the rest of the body and back to the heart in a single loop.

Answer:

A. single - loop circulation