Le due risposte sono corrette, ma nessuna delle due ti dice esattamente cosa si intende per fonte di danno.
Glossario delle Comprehensive Rules ha scritto:
Source of Damage
The source of damage is the object that dealt it. If an effect requires a player to choose a source of damage,
he or she may choose a permanent, a spell on the stack (including one that creates a permanent), or any
object referred to by an object on the stack (including a creature that assigned combat damage on the stack,
even if the creature is no longer in play or is no longer a creature). A source doesn’t need to be capable of
dealing damage to be a legal choice. See rule 419.8, “Sources of Damage.”
