When two amino acids combine and the carboxyl group of the first amino acid reacts with the amino group of the second amino acid, what is the most accurate description of the end product?
a di-peptide and carbon dioxide
a di-peptide and water
a polypeptide
a protein

When two amino acids combine and the carboxyl group of the first amino acid reacts with the amino group of the second amino acid, the end product of this combination is A di-peptide and water. 

The linking of two amino acids is accompanied by the loss of a water molecule.

Pls. see attachment for the image of the peptide-bond formation.