Some wild animals have unique features, such as stingers, claws, or the ability to change colors. These characteristics are examples of – 1. Genotypes
2. Adaptations
3. Responses
4. Stimuli

2. Adaptations

Reason:  "adaptation = a change in structure, function, or behavior by which a species or individual improves its chance of survival in a specific environment"

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.