What Is the Current Status of Research on Transfer of Training

Multiple Choice

What is the current status of research on transfer of training through brain extracts?

A) It is generally accepted that this works under a variety of conditions.
B) Transfer succeeds only in planaria: it has never worked with any other species.
C) It has been revealed that claims of such a phenomenon were based on fraud.
D) Research ended without a conclusion because the phenomenon was difficult to replicate.