To solve this question, the user needs to have knowledge of the kings of England and their historical significance. The user must recall which king was given the title "Great" to find the correct answer.

Now, let's go through each option and explain why it is right or wrong:

A. King Aethelred: This option is incorrect because Aethelred, also known as Aethelred the Unready, was not given the appellation "Great." He was known for his difficulties in ruling and defending England against Viking invasions.

B. King Henry VIII: This option is incorrect because Henry VIII, although a significant figure in English history, was not given the appellation "Great." He is more remembered for his six marriages and the English Reformation.

C. King Charles II: This option is incorrect because Charles II, also known as the Merry Monarch, was not given the appellation "Great." He is known for restoring the monarchy in England after the English Civil War.

D. King Alfred: This option is correct. King Alfred, or Alfred the Great, is the only king of England who earned the appellation "Great." He ruled in the late 9th century and is known for his military successes against the Vikings, his promotion of education, and his legal reforms.

Therefore, the correct answer is D. King Alfred.