Why does a transparent object allow s light to pass through and opaque object doesn't might be some things in there molecules which Abbsob light and and give object the color what is that thing ? because that thing is present in opaque object thus light cant pass and absent in transparent so light can pass.

It depends on the internal structure and ordering of the atoms and molecules in the object. If a particular material has a very ordered structure of molecules or atoms such as diamonds, then there is a lot of space for photons to pass through without too much scattering or absorption, or if the spacing between the molecules/atoms is comparatively large as in the case of liquids, photons can pass through. This is what we view as transparent or translucent. However solids with random and disordered molecule/atom structures absorb or reflect most of the light falling on it. This is what we view as opaque.