All of the options provided are functions of blood:
a. Oxygen transport - Blood carries oxygen from the lungs to the body's tissues.
b. Thermoregulation - Blood helps to regulate body temperature by distributing heat throughout the body and adjusting blood flow to the skin.
c. Carbon dioxide transport - Blood transports carbon dioxide, a waste product of metabolism, from the tissues back to the lungs for exhalation.
d. Coagulation - Blood plays a crucial role in the clotting process to prevent excessive bleeding when injuries occur.
In summary, all the options (a, b, c, and d) are functions of blood.