Final answer:
Insects have an open circulatory system where the hemolymph circulates freely through the body, compared to the closed circulatory system in birds, fish, and mammals.
Step-by-step explanation:
The correct answer to the question 'Which of the following organisms has an open circulatory system?' is c) Insects.
Invertebrates such as insects use an open circulatory system, where a fluid called hemolymph circulates through the body cavity and comes into direct contact with tissues. In an open circulatory system, hemolymph is pumped by a heart into the body cavity, where it baths organs directly, and then returns to the heart through openings called ostia. This is in contrast to the closed circulatory system of vertebrates, like mammals, fish, and birds, where blood is confined within arteries, veins, and capillaries. Unlike insects, birds and mammals have a highly efficient closed system that minimizes energy loss and allows for a more complex and active lifestyle.