A woodchuck tries to crack a walnut shell in two different ways--with his paws and with his teeth. The last method worked and the first did not; hence, the woodchuck will be more likely to rely on his teeth for splitting the next nut

This observation illustrates the:
a. the discrimination principle.
b. the law of practice.
c. the law of effect.
d. the Premack principle.

Answer c % correct 78 a= 2 b= 0 c= 78 d= 20 r = .27