Answer: alternative D.
Explanation: The animals that go through this process understand that everytime they drink the unusual-tasting liquid they will be injected, being that a very unpleasant series of events. They are conditioned, therefore, to be afraid of the unpleasantness of this process by associating pain to the actions that are part of it.
Future differences I think
The scientific steps is what you should follow realwged to the code of conduct