Final answer:
A Registered Hygienist Extended Functions (RDH-EF) can take impressions for cast restorations under general or direct supervision.
Step-by-step explanation:
A Registered Hygienist Extended Functions (RDH-EF) can take impressions for cast restorations under general or direct supervision. General supervision means that the supervising dentist does not need to be physically present, while direct supervision requires the dentist to be in the immediate vicinity.