Final answer:
The true statement is that smokers generally have higher needs for vitamin C than nonsmokers. Vitamins B provide support in energy production, and while vitamin C can reduce cold symptoms' severity, it does not destroy the virus.
Step-by-step explanation:
The student has asked which statement is true out of the given options regarding vitamins and the common cold. Out of the options provided, the true statement is that smokers generally have higher needs for vitamin C than nonsmokers. This is because smoking can deplete vitamin C levels, and therefore, smokers may require higher doses to counteract this effect. It is also known that vitamin C helps in the absorption of iron from the intestine and is found in foods like citrus fruits, green vegetables, and berries. While high doses of vitamin C have been shown to reduce the duration and severity of common cold symptoms, they do not destroy the virus that causes the cold.
A major role of vitamins in the B complex group is to assist in the chemical reactions that produce energy from food, rather than providing energy directly. Finally, while milk in the United States is often fortified with vitamins, it is typically vitamin D that is added to milk, not riboflavin.