Biology

Answer: A

Explanation:

Correct option: Erythropoietin is a hormone produced mainly by the kidneys.
Its role is to stimulate the bone marrow to produce red blood cells.
In chronic kidney disease, the damaged kidneys produce less erythropoietin.
As a result, the bone marrow produces fewer red blood cells, leading to anemia.
So, option A is correct.

Incorrect options:

Option B: While some substances can be lost in the urine in kidney disease, iron loss through the urine is not the primary cause of anemia in chronic kidney disea...