Final answer:
The knights of King Henry II murdered Thomas Becket, the Archbishop of Canterbury, which was a significant event in the power struggle between the English monarchy and the Church.
Step-by-step explanation:
The question pertains to the historical event involving Thomas Becket, the Archbishop of Canterbury, and the knights of King Henry II. The correct answer to what Henry's knights did to Becket is d) They murdered him.
Thomas Becket was a close friend of King Henry II and served as his Chancellor before being appointed as the Archbishop of Canterbury.
Their friendship became strained over disputes about the power of the Church versus the crown. In a moment of frustration, Henry II is said to have exclaimed in anger, possibly interpreted as a royal command by his knights, who subsequently went on to martyr Becket. Becket was martyred in Canterbury Cathedral on December 29, 1170. This act led to a widespread outcry and was a pivotal moment in the struggle between the Church and the monarchy in England.