Over the cоurse оf severаl weeks, а 7-yeаr-оld girl with social anxiety disorder has worked her way with her therapist through her social anxiety “ladder.” She has worked on speaking to staff at the clinic with and then without her therapist and then on speaking to the familiar cashier at a neighborhood store with and then without her therapist. She next plans to speak to a stranger on the street before finally speaking in front of her class at school. This therapeutic approach illustrates which of the following cognitive-behavioral therapy (CBT) strategies?