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

$A$ bullet of mass $0.02 \ kg$ travelling horizontally with velocity $250 \ ms^{-1}$ strikes a block of wood of mass $0.23 \ kg$ which rests on a rough horizontal surface. After the impact,the block and bullet move together and come to rest after travelling a distance of $40 \ m$. Find the coefficient of sliding friction of the rough surface. (Take $g = 9.8 \ ms^{-2}$)

When work is done on a body by an external force,its

Living organisms can be distinguished from non-living things on the basis of which ability,excluding exceptions?

Which among the following compounds has the highest boiling point?

$CFCl_3$ is responsible for the decomposition of ozone to oxygen. Which of the following reacts with ozone to form oxygen?