The physical basis of life is ........

What is typically used to study the structure of a plant cell?

$A.$ Mycoplasma, the smallest cells, are only $0.3 \mu m$ in length.
$B.$ Size of bacteria could be $3$ to $5 \mu m$.
$C.$ Human red blood cells are about $7.0 \mu m$ in radius.

$1 \, nm$ is equal to

The longest cell in the human body is:

The smallest size of a cell that can be seen with the naked eye is ......... (in $,\, \mu m$)