1) Is the palm of our hand opaque, transparent, or translucent when you place a lighted torch under your hand?

2) what is liguid oxygen and its uses?

Opaque objects are those objects,which do not allow to pass light through them.But here light is passed through the hand partially it means it is translucent.

Liquid oxygen is nothing but oxygen gas in liquid state.It is one of the physical forms of elementary oxygen.In commerce, liquid oxygen is classified as an industrial gas and is widely used for industrial and medical purposes. Also it is a common liquid oxidizer propellant for spacecraft rocket applications.