Answer: 4. Abnormal production of chain of Hemoglobin
Step-by-step explanation:
Anemia is a condition where the cells in the body do not get enough oxygen because the red blood cells needed to transport them are either too little or are dysfunctional.
One way the red blood cells can be dysfunctional is when they have an abnormal type of hemoglobin. Hemoglobin is necessary in red blood cells to enable to transportation of oxygen and if it is dysfunctional, oxygen will have problems being transported which would lead to anemia.