When does a duty of confidentiality arise with regard to a paralegal and their clients?

When does a duty of confidentiality arise with regard to a paralegal and their clients?
(a) When the client pays a monetary retainer
(b) When both the client and the paralegal sign a paralegal-client retainer agreement
(c) When the paralegal sends the client a client engagement letter confirming the details of the paralegal-client retainer
(d) When the paralegal-client relationship begins, which can be as soon as the initial contact if confidential information is received by the paralegal at the initial contact
Authority: Text p. 133; Paralegal Rules of Conduct Rule 3.03(1)