"In proteins, structural segments called provide flexibility that allow parts of the protein to bend, fold, or move."

The correct answer is "random coils".

Explanation:

Random coil is a type of polypeptide secondary structure comprised of conformation that do not follow an established conformation but rather are oriented randomly. These random coils conformations provides flexibility to proteins, since the lack of a particular structure (such as alpha helices or beta sheets), allows the protein to bend, fold or move.