Match the scientists in Column-$I$ with their contributions in Column-$II$:

Column-$I$	Column-$II$
$1.$ Robert Brown	$p.$ Final shape of Cell Theory
$2.$ Virchow	$q.$ Bacterial staining method
$3.$ Gram	$r.$ Unit membrane concept
$4.$ Robertson	$s.$ Discovery of nucleus

• A
  $ (1-s), (2-p), (3-q), (4-r)$
• B
  $ (1-r), (2-p), (3-q), (4-s)$
• C
  $ (1-q), (2-s), (3-p), (4-r)$
• D
  $ (1-s), (2-q), (3-p), (4-r)$