Pipes
The Circulatory System.
VEGETABLES
Yes, most arthropods have an open circulatory system, which means that their blood, called hemolymph, directly bathes their tissues. This system is less efficient at transporting oxygen compared to closed circulatory systems found in vertebrates.
The most obvious answer would be the Circulatory system; however, the Lymph system also transports material throughout the body, it could be compared to the sewer system in a city. If this is for homework though, the right answer would most assuredly be Circulatory system.
closed circulatory system (double circulatory system)
Agnatha, which includes lampreys and hagfish, have a closed circulatory system with a two-chambered heart. This system allows for more efficient distribution of oxygen and nutrients throughout the body compared to an open circulatory system.
A good and simple analogy for the circulatory system is a system of roads and towns. The main blood vessels are the motorways; the capillaries can be compared to rural country lanes. The blood cells can be compared to vehicles: red blood cells to trucks and lorries (carrying oxygen and carbon dioxide), white blood cells are best compared to police cars (protecting us from harm!). Towns, cities, villages and buildings which are passed by the vehicles represent the body cells and organs that our red blood cells unload their oxygen or CO2. This isn't a foolproof analogy, but it is a decent attempt at relating in layman's terms the function of the circulatory system.
They're both the circulatory system.
Amphibians have closed circulatory system Closed
The circulatory system
Sort of depends on just what you mean by "best", but the respiratory system certainly works the closest.
open circulatory systemclosed circulatory system.