3 Switch Wall plate to 1 Wall Plate Ceiling Fan
Splice all grounds.  Pigtail a ground to the fan-control smart switch. 
Splice all whites
Splice black A, black B, red B, and a pigtail. 
"LINE" side of your fan-control smart switch to the pigtail. 
"LOAD" side of your fan-control smart switch to Black C. 
Cap Red C.  Do not cut it off! You must cap it and you might want it later.
Cap Red D.  Ditto. 
Black and white D to fan.