In Classical Conditioning, the Unconditioned Stimulus Is

In classical conditioning, the unconditioned stimulus is:

A) an observable reaction to an environmental event that is elicited without any prior training
B) an observable reaction to an environmental event that is elicited only after training or experience
C) an environmental event that elicits an observable reaction without any prior training
D) an environmental event that only elicits an observable reaction after training or experience