I should know better by now, but I consistently underestimate Lucy. It's probably because of her size (small), age (5) and extreme cuteness of both face and voice.
Tonight, I was using a bit of bleach to try to kill some mold that was growing in her Jack-o-Lantern. Lucy came into the room, took a big whiff and said:
"Mmmmmmm. What's that smell?"
"Bleach," said I.
"Oh," she said. "I thought it was Chlorine."