Which description is an example of an allegory?

A. O. Henry's "The Ransom of Red Chief" recounts the story of two bandits who kidnap a spoiled little boy for ransom but later pay his father to take him back.
B. The Westing Game, by Ellen Raskin, tells the story of 16 people who are heirs to a large inheritance, but they must discover their benefactor’s killer in order to inherit the money.
C. "The Lady or the Tiger" by Frank Stockton is a thought-provoking story that asks a tough question: Would a woman rather see the man she loves with another woman or be mauled by a tiger?
D. William Golding's novel Lord of the Flies is a thrilling story about a group of boys surviving after a plane crash without the guidance of adults. It's also a tale about the struggle between civilization and savagery.