Step 1: Understanding the Question.
This question focuses on the type of food that supports the largest population, taking into consideration the energy and nutrition provided by each food type.
Step 2: Analyzing the Options.
(A) Fruits: While fruits are nutritious, they do not support as large a population as other food sources.
(B) Vegetables: Vegetables are important but still do not support the same population as seeds.
(C) Seeds: Correct — Seeds, such as grains, provide a high-calorie food source that supports large populations.
(D) Dairy products: Dairy products are nutritious but are less common globally compared to seeds.
Step 3: Conclusion.
The correct answer is (C) Seeds, as seeds are a major food source for many people around the world.