Answer:
Cell level organization
Step-by-step explanation:
Organisms are composed of different level of organizations like atomic level, molecular level, cell level, tissue level, organ level, system level after which whole organism if formed.
If we talk about Arachnoidiscus ehrenbergi it is one celled organism belonging to a group of algae. If we talk about human stomach it is an organ made up of several tissues which in-turn are made up of several cells.
So what is common in both?
It is a cell that is common in both, because cell is the basic unit for life of Arachnoidiscus ehrenbergi and a unit of the composition of whole stomach.
Hope it help!