For $\beta$ -Sheets,the Terms 'Parallel' and 'Antiparalllel' Refer to ___________

Multiple Choice

For $\beta$ -sheets,the terms 'parallel' and 'antiparalllel' refer to ___________.

A) the 'direction' of the associated peptide strands
B) the orientation of the amide cross-links
C) the quaternary structure of the protein
D) the orientation of the hydrogen bonding
E) the topology of the reverse turns