Jonas Salk is credited with discovery of polio vaccine. He tested the vaccine for the first time on whom?

Options :
  1. Cat
  2. Dog
  3. Himself,wife and 3 sons
  4. Sheep
Answer and Explanation :-

Answer: Option 3


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kenangan itu cuma hantu di sudut pikir. selama kita diam dan ngga berbuat apa-apa, selamanya dia tetap jadi hantu, ngga akan pernah jadi kenyataan.