Concept: Deficiency diseases:Deficiency diseases are diseases that are caused by the lack of certain essential nutrients, especially vitamins and minerals, in one's diet over a prolonged period of time.A balanced diet is extremely important for the good health of a person. Any imbalance in the diet might lead to an excess of insufficient intake of certain nutrients.Insufficient intake of a particular nutrient can lead to deficiency diseases.Vitamins:Vitamins are the essential nutrients that the body needs to function, grow and develop.The term vitamin was coined by Casimir Funk.Vitamin is the nutrient which is also known as co-enzyme.As the body does not produce vitamins itself, it must be acquired through the food we eat or in some cases through supplements. There are 13 vitamins - A, C, D, E, K, and B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, B6, B12, and folate), each of them have a different job.Vitamin A, D, E, K are fat-Soluble vitamins and are stored in fat cells while Vitamin B and C are water-soluble vitamins that are not stored in your body.Explanation:As Radha is unable to see the blackboard clearly, she is suffering from eyesight health issues.Vitamin A plays a major role in maintaining eye health by consuming Vitamin-A rich foods.Here are some foods that her doctor can suggest including milk, egg, cheese, fish, etc.Vitamin C helps in reducing the risk of cataracts. Cataracts are common in adult groups of people.Vitamin A generally helps in maintaining healthy eyesight. So, option 2 is the correct answer. Additional InformationVitamins K It is referred to as fat-soluble vitamins present in foods. It plays a major role in blood clotting, maintaining blood calcium levels, and helping in bone metabolism. Vitamin AIt is also known as retinol.It plays a crucial role in maintaining a clear cornea and helps in clear vision. Vitamin A is also a component of rhodopsin which itself is a protein that allows our eye to see in low light conditions. For a general healthy eye, vitamin-A-rich food supplements are recommended. Vitamin CIt is a water-soluble vitamin that can be found in citrus fruits and vegetables. It is an antioxidant that helps in the protection of cells against the effect of damage by free radicals. Requires in making of collagen protein, that provides structure to our eyes.Helps in reducing cataracts.Helps in preventing the progression of AMD. Vitamin DIt is a fat-soluble secosteroid.It helps in increasing intestinal absorption and retaining calcium and phosphorus which are important for building bone. Helps in the reduction of cancer growth cells.Controls the infection and also reduces inflammation.