Final answer:
The sentence that uses punctuation correctly is: 'For class, I had to read the sequel to Frankenstein: it was a real letdown compared to the original.'
Step-by-step explanation:
The correct sentence is: For class, I had to read the sequel to Frankenstein: it was a real letdown compared to the original. This sentence uses colon correctly to introduce additional information after the main clause. In this case, it is used to provide the title of the book and express the disappointment of the speaker. Colons are often used to introduce lists, explanations, or examples.
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