Why Do Amide Bonds Exist as Reasonably Stable S-Cis or S-Trans

Multiple Choice

Why do amide bonds exist as reasonably stable s-cis or s-trans isomers at room temperature?

A) These amide bonds are not stable.
B) There is partial double bond character between the carbonyl carbon and the nitrogen atom.
C) The oxygen atom is hydrogen-bonded with the nitrogen atom.
D) The side-chains can form hydrogen bonds.