Final answer:
The OTR is applying the Task-oriented approach to assess the client's ability to maintain alignment and movement while performing basic motor skills in the context of everyday activities.
Step-by-step explanation:
The approach that the OTR is applying in this scenario is the Task-oriented approach. This approach focuses on assessing the client's ability to perform everyday activities and identifies abnormal posture and movements that lead to compensation. The OTR observes the client's posture and movement while reaching or transitioning from sitting to standing. The goal is to help the client improve sitting balance and tone in the right arm after a stroke.