A practitioner 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. Schedules the practitioner prepared, which the client needs to file in its 2014 federal income tax return.

b. The engagement letter executed by the client for preparation of the 2014 federal income tax return.

c. An appraisal the practitioner prepared in connection with the 2013 federal income tax return.

d. Notes the practitioner took when meeting with the client about the 2013 and 2014 tax returns.