Answer:
Number of bacteria required 
Explanation:
Given -
Size of each bacterium 
micrometers long
These bacteria are arranged end to end.
The size of chain to be formed is equal to 
centimetres
Let us say that in forming a chain of centimetres nearly X number of individual bacterium are required.
hence, number of bacterium required to form centimetres chain can be represented as
Number of bacteria required
Answer:
Bone marrow.
Explanation:
Hematopiesis may be defined as the formation of the blood cells by the precursor stem cells. This process occurs in the bone marrow, thymus and liver.
The red blood cells are enucleated cells with the minimum span of around 120 days. These cells are processed and destroyed in the spleen. The iron is recovered from the red blood cells and sent again into the bone marrow for the production of new blood cells.
Thus, the answer is bone marrow.
