5 minites​

The answer is A.

Bacteria, which are prokaryotic cells are single-celled entities that are primitive in structure and function as they lack a membrane-bound nucleus and other organelles.

Eukaryotic cells are the cells that are complex in structure and function as they have a membrane-bound well-defined nucleus and other membrane-bound organelles.

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.