Answer:
B: "I can't believe you sewed so perfectly on your first try," Mom said, patting Juan on the back.
Step-by-step explanation:
The sentence that confirms that Juan doesn't have a lot of experience sewing is sentence B. Here, it's explicitly stated that this is Juan's first attempt sewing (... on your first try). However, despite his lack of experience, Juan sewed perfectly. The rest of the options do not contain this type of information, which is why they are incorrect.