The answer is: C. One that evoked the unspoken fears of humans
In Mary Shelley introduction for Frankenstein she said “I busied myself to think of a story, —a story to rival those which had excited us to this task. One which would speak to the mysterious fears of our nature, and awaken thrilling horror—one to make the reader dread to look round, to curdle the blood, and quicken the beatings of the heart.”