(Arid Mesa isn't a spell.)
Arid Mesa enters the battlefield tapped unless you control an enchantment.
Sacrifice a land: You gain 1 life.
: Add to your mana pool.
: Add or to your mana pool. Each opponent gains 1 life.
: Add 
to your mana pool.: Add 
or 
to your mana pool. Each opponent gains 1 life.
