As Gambriella was swinging her doll, the doll flew out of her hand and landed behind the couch out of view. Rather than look for it, Gambriella acted as though the doll no longer existed. Her behavior suggests that she is in the ___________________stage of cognitive development. (A) ​Sensorimotor. (B) ​Preoperational.(C) Concrete operational. (D) ​Formal operational.