Final answer:
The error-free sentence is about Judy finding a great deal on a used book for her accounting class as she prepares for college.
Step-by-step explanation:
The sentence that does not contain errors is:
While getting ready for college, Judy found a great deal on a used book for her accounting class.
This sentence is grammatically correct and error-free. It correctly places the clause about getting ready for college at the beginning of the sentence, establishing context, and follows with the main action that Judy found a great deal on a used book for her accounting class, which serves as the main clause with no errors in subject-verb agreement or pronoun usage.
The final answer is clear after reviewing commonly made grammar and sentence structure mistakes within the other options provided, none of which are as well-constructed and error-free as the chosen sentence.