Answer:
Option A
Step-by-step explanation:
The primary and Secondary structure are essential and present in all proteins and also include tertiary.
The primary structure is the amino acid sequence of the protein. This is the basic part of the protein.
The secondary structure are local folded structures that form within a polypeptide as a result of a couple of interactions between atoms of the backbone giving rise to the alpha helix and the beta pleated sheets in protein structures.