Final answer:
Red-orange vegetables are the best source of vitamin A among the options provided, as they contain high levels of beta-carotene, which is converted to vitamin A in the body.
Step-by-step explanation:
The best food source of vitamin A is b. red-orange veggies. Red-orange vegetables, such as carrots, sweet potatoes, and pumpkin, are rich in beta-carotene, which the body converts into vitamin A. While citrus fruits like oranges and lemons are excellent sources of vitamin C, and whole grains are good for various B vitamins and minerals, for vitamin A specifically, red-orange veggies are the ideal choice. Green leafy veggies are also a good source of vitamin A, but the question asked for the best source, which would be the red-orange vegetables.