"I know what stuff are"

Mom and I were in the basement the other day. She was looking for some things and I was just looking around at different things. I was over by the furnace and with the air conditioning on it was running. I reached down and flipped the switch off. I said, "I turned it off!" Mom told me to turn it back on and not to touch it again. I asked, "Why?" She said, "because it's not to play with and to  never touch it." I quickly replied, "But I know what stuff are."