Joe is trying to teach his dog to fetch a stick. First, he gets the dog interested in the stick by moving around the dog. When the dog starts to sniff the stick, Joe gives the dog a treat. Soon the dog is always sniffing the stick. Then Joe puts the stick near the dog’s mouth. When the dog touches it with its mouth, Joe gives the dog a treat. Then Joe only gives the dog a treat when the dog puts the stick in its mouth. Joe then throws the stick a short distance. When the dog picks up the stick with his mouth, Joe gives him a treat. Finally, Joe throws the stick and the dog picks it up and brings it back to Joe. Joe is using which technique?

A. negative reinforcement
B. tertiary reinforcement
C. shaping by successive approximations
D. contingency management

C. shaping by successive approximations