Your textbook described a classic experiment by robert rescorla that involved two groups of rats. one group of rats heard a tone just before each of 20 shocks. the second group of rats experienced the same 20 tone-shock pairings, but also experienced an additional 20 shocks that were not paired with a tone. how did the two groups differ

I believe the answer is: The rats in the first group displayed a much stronger conditioned fear response to the tone than did the rats in the second group.

This happen because the rats in the first group would automatically associate the tone with the negative physical consequences.
Making their body react due to the expectation of the physical pain every time they hear the tone.

Yes all of them are right