The correct answer is 1) Anaemia. Anemia is a condition characterized by a decrease in the number of red blood cells or a decrease in the amount of hemoglobin in the blood. This deficiency is often caused by a lack of certain nutrients, including vitamin B12.

Vitamin B12, also known as cobalamin, is essential for the production of healthy red blood cells. It plays a crucial role in the synthesis of DNA and the proper functioning of nerve cells. When there is a deficiency of vitamin B12, the body is unable to produce enough healthy red blood cells, which can lead to anemia.

Anemia caused by a deficiency of vitamin B12 is known as vitamin B12 deficiency anemia. It is more commonly seen in individuals who have a diet that lacks animal products, as vitamin B12 is primarily found in animal-based foods. Vegetarians and vegans are at a higher risk of developing this deficiency. Alert - correct answer should be option 4) Xerophthalmia.

Xerophthalmia is a disorder of the eye caused by a deficiency of vitamin A, not vitamin B12. It is characterized by dryness, night blindness, and in severe cases, ulceration and scarring of the cornea.