Q12

Robert Koch produced a set of criteria to establish whether a particular organism is the cause of a disease in an animal. The criteria are listed below but not in the correct order.

1. The microorganism must cause disease when introduced to a healthy experimental animal.
2. The microorganism must be extracted and isolated from the diseased animal and subsequently grown in culture.
3. The microorganism must be extracted from the diseased experimental animal and demonstrated to be the same microorganism that was isolated from the first diseased animal.
4. The microorganism must be found in the diseased animal, and not found in healthy animals.
   Which of the following correctly shows the order of steps required to determine the cause of a particular disease in an animal?
   A. 2, 3, 1, 4
   B. 2, 4, 1, 3
   C. 4, 2, 1, 3
   D. 4, 3, 2, 1