Final answer:
The correct option in the final answer is c. Crustaceans have an open circulatory system because their hemolymph directly bathes tissues in a body cavity, rather than being contained within a closed network of blood vessels throughout its entire circulation.
Step-by-step explanation:
The circulatory system architecture of crustaceans is considered an open system because, despite having arteries that leave the heart, the hemolymph flows into a body cavity where it directly bathes the tissues. This system is in contrast to a closed circulatory system, where blood is contained within a network of vessels separate from body tissues. In crustaceans, the hemolymph returns to the heart through openings called ostia, allowing for gas and nutrient exchange without the higher energy cost of maintaining a closed system.
The correct option in response to the original question is (c) The hemolymph directly bathes the tissues. Although crustaceans have arteries and their heart is indeed a pump, the presence of arteries is not what determines if a circulatory system is open or closed. It is the fact that after leaving the arteries, the hemolymph enters a body cavity and is not confined within blood vessels as it is in closed systems.