For a Treatment Method to Be Referred to as an Empirically

For a treatment method to be referred to as an empirically supported treatment it must have demonstrated success

A) from a large series of RCTs and a large series of single-case studies.
B) from a large series of RCTs or a large series of single-case studies.
C) from at least 2 RCTs and a large series of single-case studies.
D) from at least 2 independently conducted RCTs or a large series of single-case studies.