Which vessels return blood to the heart?

Which vessels return blood to the heart?
 a. arteries
  b. veins
  c. capillaries
  d. arterioles

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The exchange of nutrients takes place in the:
 a. capillaries.
  b. arteries.
  c. veins.
  d. venules.

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The smallest blood vessels are:
 a. veins.
  b. arteries.
  c. capillaries.
  d. arterioles.

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The blood functions to transport:
 a. hormones to organs to assist their function.
  b. red blood cells to aid in the immune process.
  c. white blood cells to conduct oxygen to the tissues.
  d. all of these choices

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Which vessel conducts oxygenated blood?
 a. superior vena cava
  b. inferior vena cava
  c. pulmonary artery
  d. aorta