Which of these nutrients is destroyed by exposure to light?

The answer to this question would be: riboflavin

Riboflavin or vitamin B2 is a member family of vitamin B which was a water-soluble vitamin. It can be found in milk but it will be degraded by sunlight. Other vitamins that can be destroyed by light would be B6 and vitamin C. Generally it would be best to avoid exposure to sunlight to keep the nutrient of your food.