(A) Packed like sardines → Refers to being crowded very close together, like sardines tightly packed in a can → (II)
(B) Make oneself scarce → Means to leave quickly or deliberately stay away from a place → (IV)
(C) A smear campaign → An organized effort to damage someone's reputation through negative publicity → (I)
(D) A slip of the tongue → An unintentional verbal mistake or error in speech → (III)
Hence, Option 3: (A) - (II), (B) - (IV), (C) - (I), (D) - (III) → This correctly matches all four idioms with their appropriate meanings → correct