Conditioned Response in Classical Conditioning

In a study on classical conditioning, researchers conditioned a group of rats to associate a specific sound with a painful electric shock. After several pairings of the sound and the shock, the rats began to exhibit a fearful response whenever they heard the sound, even in the absence of the shock. This type of learning demonstrates various principles of classical conditioning. Based on this scenario, which of the following terms best describes the rats' learned response to the sound?