Step 1: Arsenic poisoning in livestock is classically described by intense abdominal pain, a staggering gait, weakness, vomiting, rapid weak pulse with shock, and diarrhea that ends in collapse and death, so Arsenic matches (IV).
Step 2: Mercury exposure typically causes short term effects such as nausea, vomiting, diarrhea, a rise in blood pressure or heart rate, skin rashes and eye irritation, so Mercury matches (II).
Step 3: Fluoride toxicosis in cattle produces depression, weakness and ataxia along with postmortem gastroenteritis and degeneration of the renal tubular epithelium, so Fluoride matches (III).
Step 4: Lead is left with the general presentation of abdominal pain and diarrhea, so Lead matches (I).
Answer: (A) - (III), (B) - (IV), (C) - (I), (D) - (II).