Why are single-celled organisms like bacteria typically invisible without a microscope?

Because they are less complex than other life forms.

Because they do not have a defined shape or structure.

Because the entire organism consists of just one microscopic cell.

Because they only live in dark environments where they cannot be seen.

A student looking at pond water through a microscope sees a tiny, self-contained object moving independently. What is the most logical conclusion about this object?

It is a single-celled organism.

It must be a piece of a larger plant.

It is a non-living particle of sand.

It is a tiny multicellular animal.

They are both visible to the naked eye.

They are both composed of one or more cells.

They both consist of a single, complex cell.

They have an identical number of cells.

A complex organ system for respiration.

An outer shell made of minerals and rock.

A structure composed of at least one cell.

The ability to be seen without any tools.