Why the buildings are not appearing in build option?

Can you be more specific. If you are not seeing anything at all in the build menu then there is a glitch with the game. You may need to update it or reinstall (make sure your game is bound).

If certain buildings are unavailable then you may just b missing some requirement. Buildings unlock at certain levels and can required other things like gold before you can start. Tap on the building to see any requirement listed.