Tia is fascinated with the toilet. So far, her parents have caught trying to flush a stuffed animal, a toy cell phone, and a handful of dog kibble. Which sensorimotor stage is tia most likely in?

I believe the answer is: Stage 5

In the stage 5 of sensorimotor stage, children start to develop their sense of creativity. Meaning that they also start to obtain high level of curiosity, which makes them often try doing various new things that they never encounter before (eating sands, flushing things down to toilet, etc)