Final answer:
In single-celled organisms, the structure that can be found is an outer covering, which is essentially the cell membrane that protects and encloses the cell.
Step-by-step explanation:
The structure that could be found in a single-celled organism is a. outer covering. Single-celled organisms, also known as unicellular organisms, do not possess complex internal structures such as internal organs, legs and feet, or large brains, which are characteristics of multicellular organisms. Instead, they have an outer covering which can be referred to as a cell membrane or plasma membrane that encloses the cell, providing protection and regulating the movement of substances in and out of the cell.