Topics: Respiration, Immune System, Blood Cells Quiz
Why do arteries have a thick muscle layer?
A. To provide energy for the blood vessel.
B. To prevent the blood flowing backwards.
C. To help withstand the high pressure blood, also to contract to control blood flow.
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Which type of cell is found in the greatest numbers in blood?
A. Red blood cell
B. White blood cell
C. Platelets