Correct Answer: C

Rationale: Inadequate protein intake can lead to a decrease in antibody production, making individuals more susceptible to infections. Insulin (Choice A) is a hormone involved in regulating blood sugar levels, not related to protein intake. Lipoprotein (Choice B) is a type of lipid-protein complex involved in lipid transport, not directly related to antibody production. Albumin (Choice D) is a protein that helps maintain oncotic pressure and carries various substances in the blood, but it is not primarily responsible for fighting infections like antibodies.

Correct Answer: A

Rationale: The correct answer is A: 9. Nine amino acids are considered essential or indispensable because they cannot be synthesized by the body and must be obtained through the diet. These amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Choices B, C, and D are incorrect as the number of essential amino acids is specifically 9, as they are crucial for various bodily functions.

Correct Answer: D

Rationale: The correct answer is D, 'limiting.' In the analysis of the amino acid composition of foods, the amino acid that occurs in the smallest amount is referred to as the limiting amino acid. This term is used because when one essential amino acid is deficient, it limits the synthesis of proteins, making it crucial in determining protein quality. Choices A, B, and C are incorrect. 'Indispensable' and 'dispensable' refer to the essentiality of amino acids, and 'complementary' does not describe the concept of the amino acid occurring in the smallest amount.

Correct Answer: D

Rationale: The correct answer is D, eggs. Eggs are considered a high-quality protein source as they are rich in indispensable amino acids. Lentils, tofu, and peanuts also contain protein but are not as high in indispensable amino acids as eggs, making them less complete protein sources.

Correct Answer: A

Rationale: Dextrins are a type of polysaccharides formed during the breakdown of starch. Choice A is correct because dextrins are indeed polysaccharides, not the end products of starch digestion (Choice B). They are not formed in the liver (Choice C) nor rapidly excreted (Choice D).