Professor Margo Is Conducting a Twin Study Regarding Intelligence

Professor Margo is conducting a twin study regarding intelligence.Specifically,she is studying Abigail and Brenda who are identical twins.They were born to Carla and Jim and were adopted by Darma and Henry,who already had two children,Terry and Veronica.In this example,who are the identical twins' biological parents?

A) Abigail and Brenda
B) Carla and Jim
C) Darma and Henry
D) Terry and Veronica