Final answer:
The figurative language used in the sentence 'Molly had a pie in the sky idea of what college would be like' is an idiom, which is an expression with a meaning not deducible from its individual words.
Step-by-step explanation:
The phrase “Molly had a pie in the sky idea of what college would be like” uses a type of figurative language known as an idiom. An idiom is an expression whose meaning is not predictable from the usual meanings of its constituent elements, nor from the general grammatical rules of a language, and that is not a constituent of a larger expression of like characteristics. In this case, “pie in the sky” means a hope, idea, or plan that is not likely to happen or very unrealistic.
This sentence does not qualify as personification, as that would involve giving human characteristics to non-human things, nor is it a metaphor, which is a direct comparison between two unlike things without using “as” or “like.” Furthermore, it is not a simile, which makes a comparison between two things using “as” or “like.” Therefore, the most appropriate choice for this sentence is an idiom.
Given these options, the correct answer to which type of figurative language is used in the sentence is: A. idiom.