After a dog had been conditioned to salivate at the sight of meat powder, the meat powder was presented to the dog every three minutes and held just out of the dog's reach. over the course of several trials, the amount of saliva secreted by the dog decreased to zero, indicating that had occurred.

The correct answer is extinction.

Extinction refers to a concept from the psychologist, Ivan Pavlov's theory of classical conditioning. It is the process whereby, when a conditioned stimulus (CS) is no longer followed by an unconditioned stimulus (UCS), the conditioned response (CR) stops occurring or becomes 'extinct'. In this instance,when the packet of meat powder (CS) was not followed by feeding it to the dog (UCS), the dog stopped salivating (CR).