Concept:Deficiency diseases are caused by the lack of essential nutrients, like vitamins, in our diet.Explanation:Our body needs vitamins for normal functioning, and it cannot produce them sufficiently on its own. Therefore, we must get them from external sources.When there is an insufficient intake of a particular vitamin, it leads to a specific deficiency disease.The disease 'Scurvy' is a well-known example of a vitamin deficiency disease.As seen in the table, Scurvy is caused by the deficiency of Vitamin C, whose scientific name is Ascorbic acid.Answer:D. Ascorbic acid