Final answer:
Among the options provided, peanuts are the only source that does not provide complete protein, as they lack sufficient amounts of one or more essential amino acids.
Step-by-step explanation:
The question asks which of the following is not a source of complete protein: a. milk, b. soy products, c. peanuts, d. eggs. Complete proteins contain all nine essential amino acids required by the human body. While milk, soy products, and eggs are all sources of complete proteins, peanuts are not. Peanuts are a source of protein, but they do not provide adequate amounts of all the essential amino acids, making them an incomplete source of protein.