What fundamental characteristic is shared by a microscopic bacterium and a large whale?

They are both considered organisms.

They can both be seen without a microscope.

They both live exclusively in water.

An organism is described as "microscopic." What is the primary meaning of this term?

It is too small to see with the naked eye.

without the use of a special magnifying tool.

because it is transparent like glass.

unless you are very close to it.