Which of the following statements is TRUE concerning a customer who would like to transfer an account held by a broker-dealer?

a. The customer is required to use the Automated Customer Account Transfer Service (ACATS).
b. The customer is required to use the Automated Clearing House (ACH).
c. The customer is not required to use ACATS.
d. An account may only be transferred if the registered representative servicing the customer's account changes broker-dealers.