In pavlov’s original experiment with dogs, the tone was initially a(; after it was paired with meat, it became a(.
conditioned; neutral
neutral; conditioned
conditioned; unconditionedun
conditioned; conditioned

neutral; conditioned

Explanation:

Ivan Pavlov was a physiologist from Russia, who decided to investigate how the production of saliva in dogs was done in response to the dogs being fed.  

He later found out he has made remarkable discovery when he noticed that not only do dogs produce saliva when they see food, they also do the same whenever they experience any event or activity that has been associated with food by them  

He used a metronome, a device that produces audible sound or clicks, as his neutral stimulus and that did not generate any form of reaction from the dog. Pavlov then did the conditioning experiment with the meat and he clicked the metronome before presenting the meat to the dogs.  

After several attempts on this, he later decided to put out the metronome alone and the clicking of the device then caused the increase in the quantity of saliva generated by the dogs.