Why girls had a period and will be pregnant?

A period is the shedding of the inner line of the uterus to get rid of unfertilized eggs once a month. A girl can get pregnant if a sperm gets into an egg

b because they naturally adapt to their environment plz mark brainliest

explanation:

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.