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2 Removing ambiguity
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Your text is slightly off. It's actually:

Whenever a land enters the battlefield under your control, you may return target nonland permanent card from your graveyard to your hand. If that land is a Plains, you may return that nonland permanent card to the battlefield instead.

So, it's referring to the land that enters the battlefieldtriggers landfall, not the nonland permanent you're targeting in your graveyard.

Your text is slightly off. It's actually:

Whenever a land enters the battlefield under your control, you may return target nonland permanent card from your graveyard to your hand. If that land is a Plains, you may return that nonland permanent card to the battlefield instead.

So, it's referring to the land that enters the battlefield, not the nonland permanent you're targeting in your graveyard.

Your text is slightly off. It's actually:

Whenever a land enters the battlefield under your control, you may return target nonland permanent card from your graveyard to your hand. If that land is a Plains, you may return that nonland permanent card to the battlefield instead.

So, it's referring to the land that triggers landfall, not the nonland permanent you're targeting in your graveyard.

1
source | link

Your text is slightly off. It's actually:

Whenever a land enters the battlefield under your control, you may return target nonland permanent card from your graveyard to your hand. If that land is a Plains, you may return that nonland permanent card to the battlefield instead.

So, it's referring to the land that enters the battlefield, not the nonland permanent you're targeting in your graveyard.