DVI-A is analog-only and serves no purpose other than use with passive DVI-to-VGA adapters. I am not sure any GPU card has ever been made with one of those.
DVI-D is digital-only.
DVI-I is analog + digital but you can only use one mode at a time and the analog mode serves no purpose other than passive DVI-to-VGA adapters.
For 120Hz, you need to use dual-link and there is no difference between DVI-I and DVI-D for that.