(Centaur Pool isn't a spell.)
Centaur Pool enters the battlefield tapped.
, : You may put a land card from your hand onto the battlefield.
: Add or to your mana pool.
: Add to your mana pool. Put Centaur Pool on top of your library.
, 
: You may put a land card from your hand onto the battlefield.: Add 
or 
to your mana pool.: Add 
to your mana pool. Put Centaur Pool on top of your library.
