The number of essential amino acids in the human body is (b) 20. These amino acids are crucial for various physiological processes, including protein synthesis, enzyme function, and tissue repair. They cannot be synthesized by the body and must be obtained through dietary sources. Essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine, along with arginine (essential in children), and the semi-essential amino acids cysteine, tyrosine, glycine, proline, serine, asparagine, glutamine, and alanine. Ensuring an adequate intake of these amino acids is essential for maintaining optimal health and well-being.