(A) ** To cause mental or physical pain
(B) a placement on top of a vehicle
(C) beef
(D) a secret password
EXPLANATIONS BELOW
Concept note-1: -racked; racking; racks. transitive verb. : to cause to suffer torture, pain, anguish, or ruin.
Concept note-2: -a frame or shelf, often formed of bars, that is used to hold things: a vegetable rack. a plate rack. a luggage rack.
Concept note-3: -(slang, vulgar) A woman’s breasts. synonym ▲ Synonyms: see Thesaurus:breasts.
Concept note-4: -A racking pain or emotion is a distressing one which you feel very strongly.
Concept note-5: -to try very hard to think of or remember something: I’ve been racking my brain all day trying to remember her name.