Remoras are fish that attach themselves to the underside of larger organisms, such as sharks. Remoras benefit by using the shark for protection, transportation, and food. The
shark neither benefits nor is harmed. This is an example of -
mutualism
commensalism.
predation.
parasitism.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

a. an idea which cannot be disproven!

explanation:

the answer u all are looking for is 4000000000000000000000 million years.