If the tape is pre-recorded and marked Dolby, it is Dolby B. Dolby C was available to consumers while recording their own tapes, but was not used on commercial tapes. As it has a more agressive EQ curve for encoding and decoding, it will make the prerecorde3d (Dolby B) tapes sound duller if used on playback.
Dolby HX Pro is a playback only processing and is not, to my recollection, usually selectable.
Dolby HX Pro is a playback only processing and is not, to my recollection, usually selectable.