Final answer:
The CTRS should base the assessment on the observations of the client, as the client is unable to provide background information due to dementia and expressive aphasia.
Step-by-step explanation:
The CTRS should base the assessment on the observations of the client since the client is unable to provide background information due to dementia and expressive aphasia. By observing the client's behaviors, responses, and interactions, the CTRS can gather information about the client's cognitive abilities, functional limitations, and any potential areas of improvement. Observations can include assessing the client's level of engagement, verbal and non-verbal communication, social interactions, and overall functioning.