Final answer:
Vitamin A is essential for healthy skin and vision, while vitamin D is crucial for immune function and bone health. Both vitamins are needed and are not fully represented in the given options.
Step-by-step explanation:
The nutrients needed for healthy skin, vision, and immune function are vitamins and minerals, specifically, vitamin A and vitamin D. Vitamin A is essential for healthy skin, good vision, and also plays a role in bone and teeth health. It is obtained from carotenes found in plants, like carrots, which provide the pigment necessary for the body to synthesize vitamin A.
Vitamin D is crucial for immune function, as well as bone health through its role in calcium absorption and bone remodeling. The skin functions as an endocrine organ to produce the inactive form of vitamin D3 when exposed to sunlight. Furthermore, most immune cells have vitamin D receptors, indicating the vitamin's importance in immune system function. Thus, for the question of what is needed for healthy skin, vision, and immune function, the correct answer is not explicitly mentioned among the options given, as both vitamin A and vitamin D are needed to support these functions.