William harvey discovered circulation. first, as he tightened a bandage around an arm, he noticed that the fingers turned blue and cold. then, he used a less tight bandage and noticed that the hand swelled. with further research, what conclusion could he make?
a. the blood moving toward the hand contains oxygen.
b. the blood moving away from the hand picks up oxygen.
c. veins carry oxygenated blood and are deep in the skin.
d. arteries carry deoxygenated blood and are deep in the skin.

Correct A). The blood moving toward the hand contains oxygen.  

He concluded that '' the blood moving towards the hand contains oxygen''. The blood contains oxygen and nutrients that are utilized by the body to perform various cellular activities. When the band was tightened the blood circulation stop, and blood is not able to supply nutrient and oxygen to the cell, as a result of that it turns blue and cold. But when the bandage is loosened it supplies blood and nutrients that rectify the situation.

Hence, the correct answer would be option A.

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.