Answer : 4. "Vitamin B12"
Explanation :

Symptoms of vitamin B12 deficiency or folate deficiency anemia develop slowly and are similar to those of other types of anemia, such as fatigue, weakness, and pale skin. Vitamin B12 deficiency can also cause nerve damage, the main symptoms of which include tingling, loss of touch, and muscle weakness. Confusion can arise when Vitamin B12 becomes too low. Vitamin B12 deficiency anemia in the elderly can be mistaken for dementia. This happens because of similar symptoms.