Final answer:
The correct answer is a. The brother of Henry VIII who married Catherine of Aragon and died at age 15 was Arthur, marking the answer as A) Arthur. His death preceded the significant historical events involving his brother Henry VIII, including the English Reformation and the creation of the Church of England.
Step-by-step explanation:
The brother of Henry VIII who married Catherine of Aragon before dying at the age of 15 was arthur. King Arthur was the elder brother to Henry VIII and had secured a special dispensation from Pope Julius to marry Catherine, who was the widow of his late brother. Unfortunately, Arthur passed away at a young age, leaving Catherine a widow once more, which subsequently led to her marriage to Henry VIII.
After his brother's death, Henry VIII married Catherine of Aragon, but the marriage, which produced only a single surviving child, a daughter named Mary, eventually became a focal point in the shift of religious power in England. Dissatisfied with the lack of a male heir and the inability to secure an annulment from the Pope, Henry VIII created the Church of England, declaring himself its head and annulled his marriage with Catherine, marrying Anne Boleyn thereafter. This act marked the beginning of the English Reformation and changed the religious landscape of England dramatically.