In classical-conditioning situations, the is unlearned, but the is learned.

The unconditioned response is unlearned, but the conditioned response is learned. An example would be a dog salivating as a response to food. The salivation would be the conditioned response. When the dog eventually starts salivating to the rattling of a bag of dog food which it has been hearing every time before it is fed, this salivation in response to the rattling sound is the conditioned response.

D. is righta is wrong because consumers can be carnivores and omnivores not just herbivoresb is wrong because producers are plantsc is wrong because producers are plantsso d is righthope this !