According to the product life cycle theory, once a product becomes more standardized, the main competitive weapon a company has is .

Apractitioner is engaged to prepare a client's federal income tax return for 2017 and 2018. the practitioner files the 2017 return on the client's behalf and provided copies of the 2017 return and all related documents to the client. after the 2018 return is prepared, the client disputes the fees for the 2018 tax engagement, terminates the relationship, and requests all tax returns and related records. the client has not yet paid for preparation of the 2018 return. under irs circular 230, which records must the practitioner return to the client? a.) notes the practitioner took when meeting with the client about the 2017 and 2018 tax returns. b.) the engagement letter executed by the client for preparation of the 2018 federal income tax return. c.) an appraisal the practitioner prepared in connection with the 2017 federal income tax return. d.) schedules the practitioner prepared, which the client needs to file in its 2018 federal income tax return.