Between which groups is the bond formed in two amino acids?

• A
  Between the $-NH_2$ group of one amino acid and the $-COOH$ group of another amino acid.
• B
  Between the $3'-OH$ of one amino acid and the $5'-phosphate$ of another amino acid.
• C
  Between the $1'-OH$ of one amino acid and the $4'-OH$ of another amino acid.
• D
  Between the $-CONH_2$ group of one amino acid and the $-OH$ group of another amino acid.