the purpose of valves in the heart valves is to allow blood to flow only in one direction. Valves open and close on differential pressure on each side. pulmonary and the aortic valves receive blood from the ventricles and their semilunar valves allow blood to go into the arteries and prevent back flow from the artery to the ventricles.
Angiosperms have flowers only.
B to obtain oxygen
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A. Enzymes, We have an enzyme in the cells in our bodies where hydrogen peroxide is converted.
D. Amino acids
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