Final answer:
William of Orange's marriage to Mary, James II's daughter, placed him in line for the English throne, and their accession was later justified by John Locke as the Glorious Revolution.
Step-by-step explanation:
William of Orange was indeed married to James II's daughter, Mary, and consequently, he was in line for the throne of England. This statement is true. Their marriage was a significant political union which ultimately led to the overthrow of James II in what is known as the Glorious Revolution. Philosopher John Locke later justified this overthrow, which placed Mary and William on the throne, suggesting that it was a legitimate change of power since it had the support of the parliament and protected the rights of English citizens.