Indeed that is the pertinent question. The answer?
Sophie is gaining linguistic abilities in leaps and bounds. Of llate she has been hiding behind doors, or a throw rug and asking that very question. Then jumping out and proclaiming the answer. She will sometimes do this with objects, hiding them under a pillow or blanket, thenrevealing them she will triumphantly announce their discovery. I would say this is one of her first uses of syntax. She has words, but rarely puts them together.
She has a new game where she runs at me, or Carly, or Will, with two fingers extended to tickle the target. Carly and I play along, breaking out into fake laughter. Will just seems confused by the game. Sophie loves it.
Will, meanwhile, has mastered the army crawl and can cross a room and clamp his teeth on exposed power cords in seconds, if your back is turned. He is also very amused by Sophie's antics, he will sometimes just stares at her as she talks or laughs.