Concept:
Sentence rearrangement requires arranging fragments in a logical and grammatically meaningful order.
Step 1: Identify the main clause.
The clause:
can serve as the main statement.
Step 2: Connect the condition.
The phrase:
introduces a condition.
Step 3: Complete the thought.
The remaining parts fit logically as:
followed by
Step 4: Form the complete sentence.
The food poisoning took place when a chemical substance was mistaken for salt and used in the food preparation.
Step 5: Conclusion.
Hence, the correct order is: