Who proposed the theory that "Cells arise only from the pre-existing cells"?

When carbon monoxide is passed over solid caustic soda heated to $200^\circ C$,it forms

Which one of the following is more readily hydrolysed by $S_{N}1$ mechanism?

The excess pressure in a soap bubble is thrice that in another one. Then the ratio of their volumes is:

$A$ drop of liquid of diameter $2.8\, mm$ breaks up into $125$ identical drops. The change in energy is nearly ......... $ergs$ (Surface tension $= 75\, dyne/cm$)

Hairs of a shaving brush cling together when it is removed from water due to: