地

:加

到你的法术力池中。

,

:将一个0/1白色山羊衍生物放置进场。

,牺牲X个山羊:加X点任意颜色的单色法术力到你的法术力池中。 你获得X点生命。
Springjack Pasture's last ability is a mana ability. The whole ability — including the life gain — doesn't use the stack and therefore can't be responded to.
You can sacrifice any Goats you control to activate the third ability, not just Goats created by Springjack Pasture.
If you sacrifice no Goats, you'll produce no mana and you'll gain no life.