Final answer:
The factor that contributed to Philip II's decision to launch the Spanish Armada was the execution of Mary, Queen of Scots, the heir to the English throne.
Step-by-step explanation:
One of the factors contributing to Philip II's decision to launch the Spanish Armada was the execution of Mary, Queen of Scots, who was the heir to the English throne. The correct answer to the question is A) Mary, Queen of Scots. Her execution in 1587 by Elizabeth I, who was her cousin and the reigning monarch of England, removed a Catholic claimant to the throne, which further motivated Philip II to attempt to restore Catholicism in England by launching his ill-fated armada.