Answer;
Cell
Explanation;
-The biological levels of organization of living things arranged from the simplest to most complex are: organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem, and biosphere.
-Cell is the basic unit and building block of life. It is bound by a cell membrane, and possesses a nucleus which acts as its brain. Arachnoidiscus ehrenbergi is an example of diatoms which are unicellular, therefore it is a cell.
The Earth is around 4.6 billion years old. Earth has a slightly squashed sphere, measuring 7,973 miles (12,756 km) in the diameter at the equator.
Most of the water is salt water
