In His Original Studies with Dogs, Pavlov Concluded That the Salivation

In his original studies with dogs, Pavlov concluded that the salivation response had been learned because

A) dogs should have been calmed by the musical tones, not excited to the point of salivation.
B) all behaviour is learned.
C) gradual progress towards this response had been observed.
D) dogs do not naturally salivate to musical tones.