This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Poisoning, Subject name: Forensic Medicine
All are cardiotoxic except - 
Select and explain. 
A. Aconite, B. Opium, C. Oleander, D. Nicotine
B: Opium
Answer: B: Opium 
Explanation: Classification A. Based on Nature of Poison I. Corrosive a. Strong acids-- Mineral or inorganic acids, e.g. H2SO4, HCL -- Organic acids, e.g. carbolic, acetic, oxalic acid b. Strong alkalis, e.g. sodium hydroxide c. Metals, e.g. mercuric chloride, ferric chloride. II. Irritants a. Inorganic -- Non-metal, e.g. phosphorus, iodine -- Metal, e.g. arsenic, lead etc. b. Organic -- Animal, e.g. snake, scorpion -- Plant or vegetable, e.g. castor, calatropis etc. c. Mechanical, e.g. chopped hair, metal pieces etc. III. Systemic a. Cerebral poisons -- Somniferous -- Inebriants -- Stimulants -- Deliriant -- Depressant -- Psychotropics b. Spinal poisons, e.g. strychnine c. Peripheral nerve poison, e.g. curare d. Cardiac poison or cardio-toxic, e.g. aconite,oleander,nicotine e. Asphyxiants, e.g. carbon monoxide f. Nephrotoxic, e.g. mercury g. Hepatotoxic, e.g. phosphorus IV. Miscellaneous, e.g. food poisoning B. Based on Manner of Use 1. Homicidal poisons 2. Suicidal poisons 3. Accidental poisons 4. Aboifaciant poisons 5. Stupefying poisons 6. Cattle poisons 7. Arrow poisons 8. Use to fabricate injury or malingering 9. Use to cause injury 10. Use for toure C. Based on Source of Poison REF:THE SYNOPSIS OF FORENSIC MEDICINE AND TOXICOLOGY:K S NARAYANA REDDY;PAGE NO 278