Eat Hagrid's cake.

Under Hagrid's gaze, you feel like you have **** but to eat the cake. You bite down, and just manage to scrape off a sliver.

"Yum", you say, and Hagrid beams at you.

You continue talking with Hagrid, all the meanwhile nibbling on the cake. After a while, you realise that you need to head back up to the castle. Absent-mindedly, you bite down on the cake, and a large chunk breaks off. You reflexively attempt to swallow, but the piece of cake sticks inside your throat. You begin to cough.

"Harry?" Hagrid asks. "Are you alright?"

You are coughing so much that you can't reply.

"Oh, no. Oh, no", Hagrid mutters. "We need to fix you!"

He grabs you, and you lie limply in Hagrid's arms, still coughing, as Hagrad carries your up to the castle. You struggle to breathe, and pass out, just as Hagrid carries you into the Entrance Hall.