Final answer:
A pat on the back is a nonverbal way of expressing appreciation or approval. It is used to acknowledge someone's accomplishments or efforts.
Step-by-step explanation:
A pat on the back is a gesture often used to show appreciation or approval. In this context, Peter giving a pat on the back to Meg indicates that he is impressed with her work. It is a nonverbal way of expressing admiration or encouragement. The action of giving a pat on the back is commonly used to acknowledge someone's accomplishments or efforts.