Final answer:
After plaque has been removed, it takes about 24 hours for it to reform. The correct answer is C. 24 hours, highlighting the importance of regular oral hygiene practices.
Step-by-step explanation:
The student's question asks about the formation of plaque after it has been thoroughly removed. After plaque has been removed, it takes about 24 hours for it to form again. Hence, the correct answer to this question is C. 24 hours. It is important for individuals to maintain good oral hygiene by brushing and flossing regularly to prevent plaque buildup which could lead to various dental issues including cavities and gum disease.