The sentence that should be edited for pronoun clarity is:
"While Cindy and Patricia were walking down the hall, she noticed a sign on the teacher’s door."
The pronoun "she" lacks clarity because it is unclear whether it refers to Cindy or Patricia. A clearer revision could specify the subject, such as:
"While Cindy and Patricia were walking down the hall, Cindy noticed a sign on the teacher’s door." or "While Cindy and Patricia were walking down the hall, Patricia noticed a sign on the teacher’s door."