He is ill _ fever.

by

(A) of
(B) by
(C) with 
(D) None of these

🧠 Explanation:

  • Correct preposition with "ill" in context of disease is: "with".
  • We commonly say: "He is ill with fever" — this is standard English usage.
  • Other options like "of" or "by" are incorrect in this sentence structure.
  • Examples: "She is ill with the flu" / "He was ill with malaria".