Andrea has limited speech abilities. She has been attending speech therapy and is required to perform speech exercises at home. Other than her training sessions, Andrea chooses to remain essentially non- verbal. One evening, Andrea's sister called to invite Andrea on an outing. Andrea listened to her sister's invitation over the phone and nodded in excitement. Andrea's mother pointed out that her sister could not see her through the phone and that Andrea would need to speak so that her sister would know if she wanted to go. Andrea then said, "Yes, I want." This is a form of.