When we say an animal has an "open circulatory system," this means that: movement of the animal is solely responsible for moving circulatory fluid. a small amount of blood may leak out of vessels. there are no vesselsblood simply fills all spaces inside the coelom. the animal has a single-chambered heart, so blood mixes from all areas. blood flows out of vessels and into spaces or sinuses?

An open circulatory system simply means that the blood flows out of vessels and into the spaces or sinuses. Invertebrates, insects and crustaceans has an open circulatory system where pump blood goes into a hemocoel and diffusing back to the circulatory system between cells. In other animals, the heart pumps the blood into the body cavities, spaces or sinuses, where the blood surrounds the tissues.  

Ais the correct answer