β-Turns in a Peptide Chain Form a Tight Loop with Hydrogen

β-Turns in a peptide chain form a tight loop with hydrogen bonding of the carbonyl oxygen with:

A) side chain amine of lysine two amino acids down the chain.
B) amide proton on the next amino acid down the chain.
C) amide proton of the glutamine side chain.
D) amide proton of the residue three positions down the chain.
E) amide proton of asparagine side chain.