Which one is unicellular and multicellular

I:crab and II: pond organism

Pond organism is unicellular and crab is multi cellular.

The simplest level at which life exist is called the cell. Unicellular organism contain only one cell while multi cellular organisms contain more than one cell. Multi cellular organisms can be organized into various levels such as Cells>tissues> organs>organ systems> organism. Thus pond organism is unicellular under microscope and crab is multi cellular.