Which of the Following Best Illustrates Classical Conditioning

Which of the following best illustrates classical conditioning:

A) a parent tells a child he did a good job after he completes his homework early
B) a parent will not allow a child to watch TV because she broke a house rule
C) a parent makes sure to reward a child's prosocial behavior intermittently instead of continuously
D) a mother gives her toddler a snack whenever she hears the toddler's new baby sibling crying to be nursed