You had problems with potions and you spent a long time racking your brains over your homework on this intractable subject.

When you realized that you couldn’t cope on your own, you decided to ask someone for help. Who knows this subject well and can explain who will agree to help? It’s difficult to find such a person...

The thought of Cedric immediately came to your mind. Why not? He seems to be good at potions and would be happy to help, right? Therefore, you decided that it was worth asking him for help.