C.1.
My 6 yr old did the same thing when he was that age. The police came, and asked me if everything was ok, I didn't know what they were talking about, and he said a 911 call had been made from our house. That's when he ran and hid in the bedroom. The officer asked to speak to him, and he explained that calling 911 is only for when someone really needs help, if they are hurt or a bad person in your home. I'm surprised the officer didn't have that talk with him, I'm sure it happens more often than we think.
Also, if he will be starting Kindergarden this Fall, if the Mpls school district offers anything like a "Safety Town" classes like we have here. They talk about numerous topics every day and using 911 is one of them. I think it was only $25, but worth every penny of it and the kids enjoy it so much.