<span>Kind of substance besides water:
The best example of hydrogen bonding excluding water is DNA. The two strands of polymers are connected by hydrogen bonds between the nucleotide bases</span>.
The answer is intermediate, so E.
The two compounds shown indeed have tha same molecular formula, C5 H11 NO2. One of the molecules has a group NH2 and a group COOH, the other molecule has a NOO group, that makes that the two isomers have a completely different structure, with the atoms arranged in a completely different order. <span>This kind of isomers fits in the definition of structural isomers, so the answer is structural isomers.</span>
