The "Go" Sign

I was helping Sienna read her story book brought home from school. Usually the stories are made of three letter words. Today, she read out the word "stop" as if she always knows about it. "How did you learn it?" I asked. "Myself," she answered. I pulled down the shutter and asked her to look out the window. There is a stop sign at the top of the street. "It shows on every 'Stop sign'," I pointed out. Spotting it, she asked, "Where is the 'Go' sign, Mommy?"