The answer is A. For a basic reference, here's a Gatherer ruling on
Volrath, the Shapestealer:
Gatherer Ruling wrote:
8/23/2019 If another object becomes a copy of Volrath, it has the ability to become a copy of something else and it’s 7/5.
For a for detailed explanation, here's the relevant comp rule:
Comprehensive Rules wrote:
706.3. The copy’s copiable values become the copied information, as modified by the copy’s status (see rule 110.5). Objects that copy the object will use the new copiable values.
Example: Vesuvan Doppelganger reads, “You may have Vesuvan Doppelganger enter the battlefield as a copy of any creature on the battlefield, except it doesn’t copy that creature’s color and it gains ‘At the beginning of your upkeep, you may have this creature become a copy of target creature, except it doesn’t copy that creature’s color. If you do, this creature gains this ability.’” A Vesuvan Doppelganger enters the battlefield as a copy of Runeclaw Bear (a 2/2 green Bear creature with no abilities). Then a Clone enters the battlefield as a copy of the Doppelganger. The Clone is a 2/2 blue Bear named Runeclaw Bear that has the Doppelganger’s upkeep-triggered ability.