According to the international union for conservation of nature and natural resources (iucn), 73% of species have become extinct, endangered, vulnerable, or rare because of?
a. chemical pollution of water and air
b. stratospheric ozone depletion
c. overexploitation of certain species
d. alteration or destruction of the physical habitat.
e. global climate change resulting from a variety of human activities

d. alteration or destruction of the physical habitat

Explanation:

The situation with the extinction rates of the species is alarming to say the least. Around 73% of the species have gone extinct or become endangered, vulnerable, or rare. This is actually leading to a situation where the humans create a sixth mass extinction. The main reason for this are the human activities, more specifically, the alteration of the physical environment to suit the human needs, or the destruction of it. This has led to direct destruction of species, or indirect by totally destroying their habitat.

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.