Which scientist studied a thin slice of cork under a microscope?

The cell theory states that,.........

Which is the largest cell?

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 $RBCs$

The scientist who described the box-like structures with solid walls in a natural microscope is:

Which scientist explained that all cells arise from pre-existing cells?