Which of the following is true of mental imagery research?

Which of the following is true of mental imagery research?
A) Mental imagery research shows that it helps individuals to recover substantially faster from injuries.
B) Research on the use of mental imagery is exciting and looks to have potential, but the results have been largely inconclusive thus far.
C) Though research supports the notion that the use of mental imagery may be helpful in performance, there is no research indicating that brain activity exists with mental imagery alone.
D) Cases like Liu Chi Kung, the famous Chinese pianist, clearly demonstrate that mental imagery has powerful benefits.
E) Though the use of mental imagery will definitely not harm the user and is therefore recommended, there is no direct evidence that it works either.