The major reason that antiparallel beta-stranded protein structures are more stable than parallel beta-stranded structures is that:
a. parallel ones are in a slightly less extended configuration than antiparallel strands.
b. parallel ones do not have as many disulfide crosslinks between adjacent strands.
c. parallel ones do not stack in sheets as well as antiparallel strands.
d. parallel ones have fewer hydrogen bonds than antiparallel strands.
e. parallel ones have weaker hydrogen bonds between adjacent strands.