Final answer:
Tofu contains soy, which is a common food allergen. Other options like steamed rice, apples, and baked potatoes usually don't contain common allergens.
Step-by-step explanation:
The student has asked which food item among Steamed Rice, Apples, Tofu, and Baked Potatoes contains a common food allergen. The answer is C. Tofu. Tofu is made from soybeans, and soy is one of the most common food allergens, which can cause allergic reactions in individuals sensitive to it. Other common food allergens include milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and sesame. Baked potatoes, steamed rice, and apples are generally not associated with common food allergies, unless the individual has a specific allergy to those foods, which is much rarer.