Life begins above which level of organization?

The smallest part of a living organism is....

The smallest cell $= P$, the largest cell $= Q$, and the longest cell $= R$. What do $P$, $Q$, and $R$ represent in the blanks above?

The phase-contrast microscope is ..........

Arrange the following cells in an ascending order of their size and select the correct option:
$I.$ Ostrich eggs
$II.$ Mycoplasma
$III.$ Bacteria
$IV.$ Human $RBCs$

Match column-$I$ (scientists) with column-$II$ (discovery) and select the correct option.

Column-$I$	Column-$II$
$A$. Leeuwenhoek	$I$. First saw and described a living cell
$B$. Robert Brown	$II$. Presence of cell wall is unique to plant cells
$C$. Schleiden	$III$. Discovered the nucleus
$D$. Schwann	$IV$. All plants are composed of different kind of cells