How can a person donate blood and never run out of it?
a. blood components are continuously pumped by the heart.
b. blood components are continuously circulated through the blood vessels.
c. blood components are continuously produced in the bone marrow.
d. blood components are continuously digested by enzymes.

The correct answer is- C. Blood components are continuously produced in the bone marrow.

Formation of blood cells is a continuous process that occurs in the bone marrow ( a gelatinous, soft tissue present within bones) of adults.

This process is called as hematopoiesis, in which undifferentiated precursor cells ( also called stem cells) are developed and differentiated into particular blood cell type ( having specific function).

Thus, through this continuous process, all the components of blood can be replenished whenever they are required.

Therefore, when a person donates blood, he never run out of it.

his research revealed two genetically different groups of prokaryotes, which justified splitting kingdom monera into two kingdoms. the genetic and cellular differences were so great, that these two kingdoms were eventually placed into different domains in the current three-domain system.