Question

how does vitamin a support the immune system?
multiple choice
it maintains the health of epithelial tissue, which forms a barrier against infection.
it improves vision, so you can see bacteria and viruses.
it promotes the formation of free radicals.
it increases acid production in the stomach.

Explanation:

Vitamin A is crucial for maintaining the integrity of epithelial tissues. These tissues line various body surfaces (like skin, respiratory tract, digestive tract) and act as a physical barrier. A healthy epithelial tissue prevents pathogens from entering the body, thus supporting the immune system. Vision improvement (related to vitamin A's role in eyesight) is not about immune - system support in terms of fighting infections. Free radicals are generally harmful (though some have roles in immune response, but vitamin A is an antioxidant that neutralizes free radicals, not promotes their formation). Acid production in the stomach is more related to digestion (like hydrochloric acid for breaking down food) and not a direct immune - system function of vitamin A.

Answer:

It maintains the health of epithelial tissue, which forms a barrier against infection.