(Centaur River isn't a spell.)
Centaur River enters the battlefield tapped.
, : You may put a land card from your hand onto the battlefield.
: Add to your mana pool. Return Centaur River to its owner's hand.
, 
: You may put a land card from your hand onto the battlefield.: Add 
to your mana pool. Return Centaur River to its owner's hand.
