Answer:
Atrioventricular valves.
Explanation:
Heart is the muscular organ of the body and acts as the pumping organ of the body. Human heart is not bigger than the fist and the human heart is divided into four chambers.
Heart murmur may be defined as the swishing sound that are made during the blood flow. This represent the heart problem. The bicuspid valve of heart is atrioventricular valve. The damage in the atrioventricular valve causes the heart murmuring.
Thus, the answer is atrioventricular valves.
Im not 100% sure but the best answer I can give is Prokaryotes because they came to be around the time oxygen did as well.
I think the correct answer is D
Metabolizing nitrogen in prokaryotes is very important to other organisms since these prokaryotes are able to convert ammonium in the soil to nitrate and, then, the denitrifying bacteria could use the nitrate produced instead of using oxygen in their metabolism in order to release nitrogen molecules. by the denitrification process, thus completing the nitrogen cycle. Without the nitrogen metabolism in prokaryotes, the nitrogen in the atmosphere could not be used or utilized to synthesize essential organic compounds that are needed by other organisms. It is only the prokaryotes that has the ability fixing nitrogen or can do the process of nitrogen fixation.
