Final Answer:
When they were at Gringotts 3) A key fell out of Hagrid's pockets.
Step-by-step explanation:
In the scene at Gringotts, Hagrid accidentally reveals a key that falls out of his pockets. This key is a crucial element in the storyline as it is later used to access Vault 713, where a mysterious package is stored. The inclusion of this detail adds to the intrigue and sets the stage for the subsequent events in the plot.
The choice of a key as the item that fell out of Hagrid's pockets is symbolic, representing the unlocking of secrets and the beginning of Harry Potter's journey into the magical world. It serves as a tangible link between the mundane world of non-magic (Muggles) and the enchanting realm of wizardry.
This narrative device not only propels the plot forward but also emphasizes the importance of certain objects in the magical world, where even a seemingly ordinary key can hold significant magical properties. Overall, the key's inclusion in the scene at Gringotts adds depth to the storyline and contributes to the overall sense of wonder and discovery in the Harry Potter series.
So, the correct option is 3) A key.