(Secluded Plains isn't a spell.)
When Secluded Plains enters the battlefield, sacrifice it unless you pay 1 life.
Sacrifice a land: You gain 1 life.
: Add to your mana pool. If you played a land this turn, Add to your mana pool instead.
: Add 
to your mana pool. If you played a land this turn, Add 
to your mana pool instead.
