Answer : 1. "Amino acids"
Explanation :

Answer: A) Amino acids Explanation: Proteins are long chains of Amino acids. That is in brief, Amino acids are the monomers of Proteins. Amino acids are compounds which contain both an amino group and a carboxylic group. Proteins are made up of 20 essential amino acids. Monomer means a small molecule of an organic substance i.e, building block in general.