Select the correct answer from each drop-down menu. the heart is a muscular organ that pumps blood. blood that contains waste materials is brought to the heart by blood vessels. this blood enters the (left atrium, right atrium, right ventricle) and then moves down. the presence of the (atrioventricular valve, valves in the aorta, valves in the veins) prevents the backflow of blood inside the heart

1. Right atrium

2. Aortic valve. Hope this helped :p

right atrium

aortic valve.

Explanation:

before it leaves the nucleus of a eukaryotic cell, mrna is altered in the following ways: - a cap is added to the 5' end of the mrna molecule; - a poly a tail is added to the 3' end; - introns are removed and exons are spliced together.

he movement of air through earth's or any planet's atmosphere is called wind, and the main cause of earth's winds is uneven heating by the sun. this uneven heating causes changes of atmospheric pressure, and winds blow from regions with high pressure to those with low pressure.

i hope this : )