Biology

The correct answer is: D.Monomer

Explanation:

Monomers are the small molecules that join together through chemical bonds to form larger molecules called polymers.

For example:

1.Monosaccharides (like glucose) are the monomers that join to form polysaccharides (like starch or cellulose).

2.Amino acids are the monomers that link together to form proteins.

3.Nucleotides are the monomers that form nucleic acids (DNA, RNA).